opt: introduce memo.ExistsPrivate and add lazy projection column

[mgartner]

opt: introduce memo.ExistsPrivate and add lazy projection column

This commit introduces the memo.ExistsPrivate struct, which wraps the memo.SubqueryPrivate struct. This new private struct has a column that is used during the execbuilder phase if the Exists subquery is planned as a lazily-evaluated routine. By adding this column to the Exists expression, we can avoid the anti-pattern of creating a new column ID in the execbuilder. This will be beneficial in future commits in which execbuilder will rely on knowing the maximum column ID for a query plan before it begins constructing execution nodes.

Release note: None

opt: move WasLimited from SubqueryPrivate to ExistsPrivate

The WasLimited field is only used for Exists subqueries, so it has been moved from SubqueryPrivate to ExistsPrivate.

Release note: None

opt: remove IntroduceExistsLimit rule

This rule has been superseded by the ConvertUncorrelatedExistsToCoalesceSubquery rule. Since that rule was introduced, IntroduceExistsLimit should have never matched.

Release note: None

[blathers-crl[bot]]

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

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

[cockroach-teamcity]

This change is 

[mgartner]

This change is a prerequisite for the changes in #119095.

[mgartner]

The diff is quite large, but most of it is changes to column IDs in optimizer tests. I'm happy to walk through all the changes if that'd be helpful.

[mgartner]

TFTR!

bors r+

[craig[bot]]

Build succeeded:

• Bazel Essential CI (Cockroach)