Simplify percentile_cont for 0/1 percentiles

[kumarUjjawal]

Which issue does this PR close?

• ClosesSimplify percentile_cont to min/max when percentile is 0 or 1 #18108

Rationale for this change

Literal 0/1 percentiles don’t need percentile buffering; using min/max keeps results identical.

What changes are included in this PR?

• Add a simplify hook so percentile_cont(..., 0|1) rewrites to min/max, preserving distinct/filter/null handling and casting ints to Float64.
• Add targeted tests for the rewrite and for the no‑rewrite path.

Are these changes tested?

Added tests

Are there any user-facing changes?

[2010YOUY01]

I suggest to add some tests in sqllogictesthttps://github.com/apache/datafusion/tree/main/datafusion/sqllogictest

It should run some SQL queries that this optimization is applicable, and we first ensure the result is expected, and also do a EXPLAIN to ensure such optimization is applied.

In fact, we can move most of the test coverage to sqllogictests, instead of unit tests here. The reason is:

1. SQL tests are simpler to maintain
2. The SQL interface is more stable, while internal APIs may change frequently. As a result, good test coverage here can easily get lost during refactoring.

[kumarUjjawal]

I kept the unit tests along with the new sql test in the sqllogictest. Should I remove the unit tests or is it okay?

[Jefffrey]

We should remove the unit tests if they duplicate the sqllogictests

[2010YOUY01]

We should remove the unit tests if they duplicate the sqllogictests

+1 unless there are something can't be covered by slt tests

[Jefffrey]

Thanks for picking this up. Have a few suggestions to simplify the code

[Jefffrey]

We should remove the unit tests if they duplicate the sqllogictests

[Jefffrey]

Thanks @kumarUjjawal