feat: add a config to disable subquery_sort_elimination

[haohuaijin]

Which issue does this PR close?

• Closes [DISCUSSION] Sorts being removed from subqueries #15886

Rationale for this change

• see [DISCUSSION] Sorts being removed from subqueries #15886 (comment)

What changes are included in this PR?

• Added a new optimizer config option: datafusion.sql_parser.enable_subquery_sort_elimination
• Added a SessionConfig builder method: with_enable_subquery_sort_elimination(...)
• Updated SQL relation planning so subquery/CTE ORDER BY elimination only happens when this config is enabled
• Kept the current behavior as the default to avoid changing existing behavior unexpectedly

Are these changes tested?

Added SQL integration tests that verify:

• subquery ORDER BY is removed by default
• subquery ORDER BY is preserved when enable_subquery_sort_elimination is set to false
• add slt test case

Are there any user-facing changes?

no

[asolimando]

Nice improvement!

In Apache Calcite we had a similar discussion a while ago (CALCITE-4160 for the details) and we reached the same conclusion, preserving ordering for subqueries is an optional feature and it's technically safe to always remove it, but it's good to let the user control this behavior.

There is a typo in the PR title where "disalbe" should be "disable", as this goes into the commit message we should fix it before merging.

Nit: it would be nice to have an SLT test with SET datafusion.sql_parser.enable_subquery_sort_elimination = false in addition to the unit tests, to check if the user-facing propagation works as expected.

[haohuaijin]

thanks for your reviews @asolimando and the information from Apache Calcite, i added the .slt test case

[alamb]

Makes sense to me -- thank you @haohuaijin