Implement check for sufficient execution stack. Needed to fix Unity case 1263270.

Enable across platforms and expose to embedding API.

Expose mono_class_is_open_constructed_type to Unity to allow us to ch…

Fix Incorrect UTC offset during DST transition (case 1288231)

Expose mono_class_is_open_constructed_type to Unity to allow us to check to see if the class is not yet fully instantiated prior to asttempting to call mono_object_new on it.

* Also cleaning up a minor leak of a MonoError in mono_unity_class_inflate_generic_class

Corrects an issue where for the hour after the DST transition, the
local UTC offset was listed.  The UTC offset was the DST offset
instead of the standard time offset.

The runtime library captures this an ambiguous time.  That is
the local time that occurs twice - once in DST then once in standard
time.  If DST is an extra 1:00 a.m. offset and ends at 2:00 a.m., 1:00 a.m.
to 1:59:59.9999.... occurs twice.  First in DST then again in standard
time.

The classlibs had this incorrect - they did not consider 1:00 a.m. an
ambiguous time, and considered 2:00 a.m. ambiguous.  However it should
be reversed.  1:00 a.m. occurs twice, but 2:00 a.m. only occurs once.
The instance we would hit 2:00 a.m. DST, we instantaneous switch to
1:00 a.m. standard.

The classlibs were also not recording enough information to record
which side of DST a local time was.  When converting a time from UTC,
or using DateTime.Now an internal flag, IsAmbiguousDaylightSavingTime,
should be set if the time is an ambiguous local time that is on the
DST side of the transition.  The classlibs were calling
TimeZone.IsAmbigousTime which has a wider defintion for ambiguous
time that the IsAmbiguousDaylightSavingTime should have.  It returns
true for local times on either side of DST.  So a new method
IsAmbiguousLocalDstFromUtc was added to check this case.

The classlibs were also not checking the IsAmbiguousLocalDstFromUtc
flag when getting the UTC offset for a local time.  So a check
was inserted in two locations to correct for that.

Some tests has to be updated to reflect these new definitions of when
DST starts and ends and which times are ambiguous.  These also account
for some test changes required by cherry-picked changes to
TimeZoneInfo.cs where the corresponding test changes were not
cherry-picked.  Some of those changes where in PR's that updated to
the CoreFx TimeZoneInfo class.

All these changes have been verified against the behavior of the
.Net Framework and they match.

Fix case 1288231:
Mono: Fix incorrect UTC offset during daylight savings time transitions

Addresses an issue with jumping into DST for some time zones when the incorrect date-time offset is returned for date-time in UTC (which comes from DateTime.Now). The fix is to just check if the incoming date-time is in UTC.

Also added a set of tests for some time zones to verify jumping into DST in general.

Fixes https://github.com/mono/mono/issues/16395

Fixes https://github.com/mono/mono/issues/16742

When a datetime appears in range of [end_of_DST_period - Daylight_delta; end_of_DST_period] it's not DST and should return base offset.

Fixes #9664.

Update Readme [skip ci]

Update mbe used for mono builds

Fix race condition in WaitAnyWithSecondMutexAbandoned test. (case 1288953)

There is a small race condition during the completion of a native thread join
call. During that period of time the tid is no longer included on the
internal list tracking joinable threads so a thread that will join on the
tid while another thread (like the finalizer thread) is waiting on native
join to complete for the same tid, will cause the managed Thread.Join call
to complete before the native join call has completed. This race could cause
issues on some OS:es that clear's up some thread resources, like abandoned
mutexes when the thread has exited. This race is hit by WaitAnyWithSecondMutexAbandoned
since the call to Thread.Join will return before the thread owning the mutex
has terminated meaning that it doesn't get ownership of the abandoned mutex
as assumed by the test.

Fix makes sure Thread.Join won't complete until native thread join is complete.
Increasing the join timeouts in the test also eliminates a timeout error making it
harder to hit the problematic code path, primarily during reproduction
in the debugger.

Fix also switch to coop mutex for joinable threads.

CreateNLSocket and CloseNLSocket should return gpointer (#15408) (case 1292368)

In managed, these functions are used as `static external IntPtr`. This means that previously on arm64 the top bits of the return value were garbage. A comparison with 64-bit -1 like in LinuxNetworkChange.EnsureSocket would never be true, which was causing us to hit other assertions in the runtime.
Co-authored-by: NAleksey Kliger <alklig@microsoft.com>

Allow different enums as return type in CreateDelegate (case 1288796)

Allow `CreateDelegate` to have return type covariance with methods that
return `enum` or `int` types.

This is from the upstream change at https://github.com/mono/mono/commit/122494330d635205b0a8766deaeafd0d79bd3d60.

After adding the concept of a pending threads join list boehm was not…

After adding the concept of a pending threads join list boehm was not removing the threads from that list on detach as sgen was in sgen_client_thread_detach_with_lock. This change brings boehm in line with sgen to remove threads from the pending join list on detach to avoid waiting the full 2 seconds on runtime shutdown. (case 1295072)

[TermInfo] support new file format terminfo2 introduced with ncurses6.1

These changes are applied from upstream Mono at https://github.com/mono/mono/pull/7308/commits/e25f5c321573b677ab9edcb88833ef40d267026c.

They correct an exception that happens on Linux like this:

```
System.TypeInitializationException: The type initializer for 'System.Console' threw an exception. ---> System.TypeInitializationException: The type initializer for 'System.ConsoleDriver' threw an exception. ---> System.Exception: Magic number is wrong: 542
  at System.TermInfoReader.ReadHeader (System.Byte[] buffer, System.Int32& position) [0x0008d] in /Users/bokken/build/output/Unity-Technologies/mono/mcs/class/corlib/System/TermInfoReader.cs:134
  at System.TermInfoReader..ctor (System.String term, System.String filename) [0x0005f] in /Users/bokken/build/output/Unity-Technologies/mono/mcs/class/corlib/System/TermInfoReader.cs:97
  at System.TermInfoDriver..ctor (System.String term) [0x00055] in /Users/bokken/build/output/Unity-Technologies/mono/mcs/class/corlib/System/TermInfoDriver.cs:164
  at System.ConsoleDriver.CreateTermInfoDriver (System.String term) [0x00000] in /Users/bokken/build/output/Unity-Technologies/mono/mcs/class/corlib/System/ConsoleDriver.cs:73
  at System.ConsoleDriver..cctor () [0x0004d] in /Users/bokken/build/output/Unity-Technologies/mono/mcs/class/corlib/System/ConsoleDriver.cs:57
```

Fixing an issue with System.XML depending on writing/reading from the registry

Pulling in change https://github.com/mono/mono/pull/12008/files which removes the registry as a dependecy for system.xml

Run codesign after otool

Ensure special static slots respect alignment (case 1266322)

Without proper alignment, this may lead to reference types
being stored at non-pointer aligned offsets. Among other
issues this may lead to the GC not scanning those pointers
properly.

Fix JIT on macOS Big Sur beta 6 when running on Apple silicon

Wait on runtime threads to park on joinable thread list during shutdown. (case 1275345)

Sign binaries after lipo-ing them since lipo drops signature added by the linker. Also, use JIT entitlement for signing executables.

Try to copy monodis into monodistribution/bin dir