release-25.1: opt: add new optimizer session settings

[mgartner]

Backport:

• 1/1 commits from "opt: add optimizer_prefer_bounded_cardinality session setting" (opt: add optimizer_prefer_bounded_cardinality session setting #139985)
• 1/1 commits from "opt: add optimizer_min_row_count session setting" (opt: add optimizer_min_row_count session setting #140065)

Please see individual PRs for details.

/cc @cockroachdb/release

Release justification: Optimizer changes gated behind session settings.

[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 

[rytaft]

Reviewed 14 of 14 files at r1, 20 of 20 files at r2, all commit messages.
Reviewable status: complete! 1 of 0 LGTMs obtained (waiting on @yuzefovich)

[yuzefovich]

Reviewed 14 of 14 files at r1, 19 of 20 files at r2, all commit messages.
Reviewable status: complete! 1 of 0 LGTMs obtained

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pkg/sql/opt/props/statistics.go line 145 at r2 (raw file):

		s.RowCount = 0
	} else if r := s.RowCount * selectivity.AsFloat(); r < s.minRowCount {
		s.Selectivity.Multiply(MakeSelectivityFromFraction(s.minRowCount, s.RowCount))

Just to double check my understanding here. If we were to apply selectivity to s, the row count would get below minRowCount, so we don't want to do that. We update RowCount to minRowCount to not go below the defined lower bound; we also need to keep s.Selectivity in sync with s.RowCount, so we update the selectivity accordingly. Right?

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pkg/sql/vars.go line 3776 at r2 (raw file):

				return err
			}
			// Note that we permit fractions above 1.0 to allow for giving

nit: copy-pasted comment isn't applicable here :)