Standardize APPROX_PERCENTILE_CONT / PERCENTILE_CONT and similar aggregation functions

[Dandandan]

Is your feature request related to a problem or challenge?

After https://github.com/apache/datafusion/pull/11721/files we handle nulls in APPROX_PERCENTILE_CONT by removing them before computing the percentile.
This is the default behaviour of PostgreSQL, Spark, etc.

However the syntax of the current aggregate functions is confusing for APPROX_PERCENTILE_CONT, as it supports IGNORE NULLS | RESPECT NULLS

Describe the solution you'd like

Come up with a plan to bring the syntax / semantics of APPROX_PERCENTILE_CONT and PERCENTILE_CONT and similar aggregations closer to PostgreSQL and others by (one or more).

• Supporting something like PostgreSQL/Spark/Snowflake syntax: SELECT percentile_cont(<fraction double precision>) WITHIN GROUP (<sort_expression>)
• Disabling specifying IGNORE NULLS | RESPECT NULLS for aggregations functions where they do not make sense / are not supported.
• Comparing results against other engines

Describe alternatives you've considered

No response

Additional context

No response

[samuelcolvin]

See pydantic/logfire#433, support for WITHIN GROUP would be great.

[Garamda]

take
(cf. #12824)

[Garamda]

@Dandandan Would you assign this task to me?

[Garamda]

PR is ready to get review : #13511

cc. @Dandandan