release-23.2: implement generic query plans

[mgartner]

Backport:

• 1/1 commits from "sql: add plan_cache_mode session setting" (sql: add plan_cache_mode session setting #125708)
• 2/2 commits from "opt: add ConvertSelectWithPlaceholdersToJoin exploration rule" (opt: add ConvertSelectWithPlaceholdersToJoin exploration rule #125795)
• 2/2 commits from "opt: improve stats for filters with placeholder equalities" (opt: improve stats for filters with placeholder equalities #125808)
• 1/1 commits from "opt: add generic query plan tests with partial indexes" (opt: add generic query plan tests with partial indexes #125871)
• 3/3 commits from "sql: implement plan_cache_mode=force_generic_plan" (sql: implement plan_cache_mode=force_generic_plan #126528)
• 1/2 commits from "sql: implement plan_cache_mode=auto" (sql: implement plan_cache_mode=auto #126863)
• 2/2 commits from "opt: optimize generic query plans with stable expressions" (opt: optimize generic query plans with stable expressions #125814)
• 1/1 commits from "sql: require an enterprise license to use generic query plans" (sql: require an enterprise license to use generic query plans #127214)
• 1/1 commits from "sql: add telemetry counters for generic query plans" (sql: add telemetry counters for generic query plans #127897)

Please see individual PRs for details.

/cc @cockroachdb/release

---

Release justification: New feature gated behind session setting.

[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.
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• Backports should not add new functionality (except as defined
  here).
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  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.
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  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.

[blathers-crl]

Your pull request contains more than 1000 changes. It is strongly encouraged to split big PRs into smaller chunks.

_{🦉 Hoot! I am a Blathers, a bot for CockroachDB. My owner is dev-inf.}

[cockroach-teamcity]

This change is 

[DrewKimball]

Reviewed 8 of 8 files at r1, 7 of 7 files at r2, 5 of 5 files at r3, 1 of 1 files at r4, 6 of 6 files at r5, 1 of 1 files at r6, 2 of 2 files at r7, 1 of 1 files at r8, 22 of 22 files at r9, 7 of 7 files at r10, 1 of 1 files at r11, 5 of 5 files at r12, 18 of 18 files at r13, 3 of 3 files at r14, all commit messages.
Reviewable status: complete! 1 of 0 LGTMs obtained (waiting on @rytaft and @yuzefovich)

[mgartner]

I've added one of the commits from #129050.

[rytaft]

Reviewed 8 of 8 files at r1, 7 of 7 files at r2, 5 of 5 files at r3, 1 of 1 files at r4, 6 of 6 files at r5, 1 of 1 files at r6, 2 of 2 files at r7, 1 of 1 files at r8, 22 of 22 files at r9, 7 of 7 files at r10, 1 of 1 files at r11, 5 of 5 files at r12, 18 of 18 files at r13, 3 of 3 files at r14, 10 of 10 files at r15, all commit messages.
Reviewable status: complete! 1 of 0 LGTMs obtained (and 1 stale) (waiting on @yuzefovich)