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)

The IMemoryPool interface was removed in ORCA to remove an unnecessary
abstraction layer and avoid costly casting.

Corresponding ORCA commit: e64a2b42

Bumps ORCA version to 3.46.0
Authored-by: NChris Hajas <chajas@pivotal.io>

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>

It's an error in standard C - at least in older standards - to typedef
the same type more than once, even if the definition is the same. Newer
versions of gcc don't complain about it, but you can see the warnings
with -pedantic (among a ton of other warnings, search for "redefinition").

To fix, remove the duplicate typedefs. The ones in src/backend/gpopt and
src/include/gpopt were actually OK, because a duplicate typedef is OK in
C++, and those files are compiled with a C++ compiler. But many of the
typedefs in those files were not used for anything, so I nevertheless
removed duplicate ones there too, that caught my eye.

In gpmon.h, we were redefining apr_*_t types when postgres.h had been
included. But as far as I can tell, that was always - all the files that
included gpmon, included postgres.h directly or indirectly before that.
Search & replace the references to apr_*_t types in that file with the
postgres equivalents, to make it more clear what they actually are.

* Add 'const' to arguments of some functions. While we're at it, remove the
duplicate extern declaration of FaultInjector_InjectFaultIfSet from
gpdbdefs.h.

* pstrdup() constants passed to makeString(). I think the lack of copy
was harmless, but makeString() explicitly says that the caller should make
a copy, and all other callers seem to obey that, so better safe than sorry.