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>

This allows removing all the code in CTranslatorDXLToPlStmt that tracked
the parent of each call.

I found the plan node IDs awkward, when I was hacking on
CTranslatorDXLToPlStmt. I tried to make a change where a function would
construct a child Plan node first, and a Result node on top of that, but
only if necessary, depending on the kind of child plan. The parent plan
node IDs made it impossible to construct a part of Plan tree like that, in
a bottom-up fashion, because you always had to pass the parent's ID when
constructing a child node. Now that is possible.