The canonical config file is in src/backend/gpopt/.clang-format (instead
of under the non-existent src/backend/gporca), I've created one (instead
of two) symlink, for GPOPT headers. Care has been taken to repoint the
symlink to the canonical config under gpopt, instead of gpopt as it is
under HEAD.

This is spiritually a cherry-pick of commit 2f7dd76c.
(cherry picked from commit 2f7dd76c)

- Fix "missing prototype" warnings
- Fix "generalized initializer lists are a C++ extension" warning

funcs.cpp:43:1: warning: no previous prototype for function 'DisableXform' [-Wmissing-prototypes]
DisableXform(PG_FUNCTION_ARGS)
^
funcs.cpp:76:1: warning: no previous prototype for function 'EnableXform' [-Wmissing-prototypes]
EnableXform(PG_FUNCTION_ARGS)
^
funcs.cpp:109:1: warning: no previous prototype for function 'LibraryVersion' [-Wmissing-prototypes]
LibraryVersion()
^
funcs.cpp:123:1: warning: no previous prototype for function 'OptVersion' [-Wmissing-prototypes]
OptVersion()
^
4 warnings generated.

CTranslatorDXLToScalar.cpp:730:9: warning: generalized initializer lists are a C++11 extension [-Wc++11-extensions]
        return { .oid_type = inner_type_oid, .type_modifier = type_modifier};

As part of moving away from Hungarian notation in the GPORCA codebase,
the integration points between GPORCA and GPDB in the translator have
been renamed to the new convention used in GPORCA. The libraries
currently updated to the new notation in GPORCA are Naucrates and GPOS.
The new naming convention is a custom version of common C++ naming
conventions. The style guide for this convention can be found in the
GPORCA repository.

Also bump ORCA version to 2.69.0
Co-authored-by: NShreedhar Hardikar <shardikar@pivotal.io>
Co-authored-by: NMelanie Plageman <mplageman@pivotal.io>
Co-authored-by: NEkta Khanna <ekhanna@pivotal.io>
Co-authored-by: NAbhijit Subramanya <asubramanya@pivotal.io>
Co-authored-by: NSambitesh Dash <sdash@pivotal.io&gt;&lt;Paste>
Co-authored-by: NDhanashree Kashid <dkashid@pivotal.io>
Co-authored-by: NOmer Arap <oarap@pivotal.io>

As pointed out by Heikki, maintaining another variable to match one in
the database system will be error-prone and cumbersome, especially while
merging with upstream. This commit initializes ORCA with a pointer to a
GPDB function that returns true when QueryCancelPending or
ProcDiePending is set. This way we no longer have to micro-manage
setting and re-setting some internal ORCA variable, or touch signal
handlers.

This commit also reverts commit 0dfd0ebc "Support optimization interrupts
in ORCA" and reuses tests already pushed by 916f460f and 0dfd0ebc.

To support that, this commit adds 2 new ORCA APIs:
- SignalInterruptGPOPT(), which notifies ORCA that an abort is requested
  (must be called from the signal handler)
- ResetInterruptsGPOPT(), which resets ORCA's state to before the
  interruption, so that the next query can run normally (needs to be
  called only on the QD)

Also check for interrupts right after ORCA returns.

There are other functions in the same file that reference the same
functions, so we don't need this to hint the linker anymore.

These were initialized by constructors earlier. To pass any parameters
for initializing GPOPT or any of its dependendencies, we need to do that
explicitly.