Add native support for acosh function

[weimingdiit]

Describe the bug
Add native support for Spark acosh(expr) through Auron’s standard builtin ScalarFunction path.

Concretely:

• convert Spark Acosh expressions in NativeConverters
• add ScalarFunction::Acosh in auron.proto
• map ScalarFunction::Acosh in planner.rs
• reuse the existing backend acosh implementation instead of introducing a custom extension function

[slfan1989]

@weimingdiit Could we add some additional details to this issue description? Thank you!

[weimingdiit]

@weimingdiit Could we add some additional details to this issue description? Thank you!
@slfan1989 Sure, I’ll update the issue description with more details. Thanks for the suggestion!