release-23.1: opt: fix bugs in plan gist decoding

[blathers-crl]

Backport 2/2 commits from #109627 on behalf of @mgartner.

/cc @cockroachdb/release

---

opt: fix plan gist decoding of inverted filters

Details about inverted filter nodes are not encoded in plan gists. The
plan gist decoder incorrectly assumed there were some details encoded,
and would raise an internal error whenever decoding a plan gist with an
inverted filter. This commit fixes the incorrect assumption to prevent
the internal error.

Fixes #108979

There is no release not because plan gists are an undocumented feature.

Release note: None

opt: fix plan gist decoding internal error

This commit fixes some cases where crdb_internal.decode_plan_gist
could raise internal index-out-of-bound errors when given incorrectly
formed input.

Fixes #109560

Release note: None

---

Release justification: Low-risk bug fix.

[blathers-crl]

Thanks for opening a backport.

Please check the backport criteria before merging:

• Backports should only be created for serious
  issues or test-only changes.
• Backports should not break backwards-compatibility.
• Backports should change as little code as possible.
• Backports should not change on-disk formats or node communication protocols.
• Backports should not add new functionality (except as defined
  here).
• Backports must not add, edit, or otherwise modify cluster versions; or add version gates.
• All backports must be reviewed by the owning areas TL. For more information as to how that review should be conducted, please consult the backport
  policy.

If your backport adds new functionality, please ensure that the following additional criteria are satisfied:

• There is a high priority need for the functionality that cannot wait until the next release and is difficult to address in another way.
• The new functionality is additive-only and only runs for clusters which have specifically “opted in” to it (e.g. by a cluster setting).
• New code is protected by a conditional check that is trivial to verify and ensures that it only runs for opt-in clusters. State changes must be further protected such that nodes running old binaries will not be negatively impacted by the new state (with a mixed version test added).
• The PM and TL on the team that owns the changed code have signed off that the change obeys the above rules.
• Your backport must be accompanied by a post to the appropriate Slack
  channel (#db-backports-point-releases or #db-backports-XX-X-release) for awareness and discussion.

Also, please add a brief release justification to the body of your PR to justify this
backport.

[cockroach-teamcity]

This change is 

[mgartner]

This backport is motivated by #133645.

[DrewKimball]

Reviewed 2 of 2 files at r1, 4 of 4 files at r2, all commit messages.
Reviewable status: complete! 1 of 0 LGTMs obtained (waiting on @mgartner)