feat: support exp and refactor pow

[lmatz]

I hereby agree to the terms of the RisingWave Labs, Inc. Contributor License Agreement.

What's changed and what's your intention?

As per the title. Since only float64 is supported, let the cast happen in frontend.

Checklist

• I have written necessary rustdoc comments
• I have added necessary unit tests and integration tests
• I have added fuzzing tests or opened an issue to track them. (Optional, recommended for new SQL features). Sqlsmith: Sql feature generation #7934
• I have demonstrated that backward compatibility is not broken by breaking changes and created issues to track deprecated features to be removed in the future. (Please refer to the issue)
• All checks passed in ./risedev check (or alias, ./risedev c)

Documentation

- [ ] My PR DOES NOT contain user-facing changes.

Click here for Documentation

Types of user-facing changes

Please keep the types that apply to your changes, and remove the others.

• SQL commands, functions, and operators

Release note

Support function exp. The decimal version is not supported.

#7725

[github-actions]

license-eye has totally checked 2765 files.

Valid	Invalid	Ignored	Fixed
1311	1	1453	0

Click to see the invalid file list

• src/expr/src/vector_op/exp.rs

[xiangjinwu]

rest lgtm

[codecov]

Codecov Report

Merging #7971 (afe0801) into main (0ce9d72) will decrease coverage by 0.01%.
The diff coverage is 20.00%.

@@            Coverage Diff             @@
##             main    #7971      +/-   ##
==========================================
- Coverage   71.35%   71.34%   -0.01%     
==========================================
  Files        1120     1121       +1     
  Lines      180827   180839      +12     
==========================================
- Hits       129024   129017       -7     
- Misses      51803    51822      +19     

Flag	Coverage Δ
rust	71.34% <20.00%> (-0.01%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
src/expr/src/expr/build_expr_from_prost.rs	40.54% <ø> (ø)
src/expr/src/expr/expr_binary_nonnull.rs	52.26% <0.00%> (-0.24%)	⬇️
src/expr/src/expr/expr_unary.rs	60.80% <0.00%> (-0.89%)	⬇️
src/expr/src/vector_op/arithmetic_op.rs	42.91% <0.00%> (+0.82%)	⬆️
src/expr/src/vector_op/exp.rs	0.00% <0.00%> (ø)
src/expr/src/sig/func.rs	93.96% <100.00%> (+0.02%)	⬆️
src/frontend/src/binder/expr/function.rs	89.26% <100.00%> (+0.05%)	⬆️
src/batch/src/executor/group_top_n.rs	68.23% <0.00%> (-6.48%)	⬇️
src/object_store/src/object/mem.rs	86.48% <0.00%> (-0.39%)	⬇️
src/object_store/src/object/mod.rs	50.31% <0.00%> (-0.22%)	⬇️
... and 5 more

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