[AURON #2126] Add native support for acosh function

[weimingdiit]

Which issue does this PR close?

Closes # #2126

Rationale for this change

Spark Acosh expressions were not wired into Auron’s standard builtin scalar function conversion path, so acosh(expr) could not be planned through the native backend.

This change follows the existing ScalarFunction flow used by other builtin math functions such as acos, asin, and atan: Spark expression conversion in NativeConverters, protobuf enum registration in auron.proto, and planner mapping in planner.rs. This keeps acosh aligned with the current architecture instead of introducing a custom extension function path.

What changes are included in this PR?

This PR:

adds Spark Acosh expression conversion in NativeConverters
introduces ScalarFunction::Acosh in auron.proto
maps ScalarFunction::Acosh in planner.rs
enables acosh(expr) through the standard builtin ScalarFunction chain

Are there any user-facing changes?

No.

How was this patch tested?

CI.

[slfan1989]

@weimingdiit Thank you for your contribution! Could we add some unit tests？

[weimingdiit]

@weimingdiit Thank you for your contribution! Could we add some unit tests？

@slfan1989 Thanks for your comment. I’ve added the ut. Could you please take another look?

[slfan1989]

@weimingdiit Thanks for the contribution! Merged into the master.

[weimingdiit]

@slfan1989 Thanks for your review and merge.