reuse code utils::optimize_children but affect inline.

[jackwener]

Which issue does this PR close?

part of #4120.

It's different from #4119 , this PR make rewrite_expr become member function which was inline function originally.
refactor it may affect inline. I don't ensure it, so I seperately new a PR. If this PR don't look like good, we can close it.

Rationale for this change

What changes are included in this PR?

Are there any user-facing changes?

[alamb]

This refactor looks good to me -- thank you @jackwener

cc @waynexia who originally contributed this pass in #792

I'll wait at least 24 hours to see if they want to respond or have additional time to review

[waynexia]

Thanks @alamb for mention me.

This change also looks good to me. I have no opinion with inlining (and can't talk what will LLVM do in the end 😂). So let's just go ahead

[alamb]

Thanks again @jackwener

[ursabot]

Benchmark runs are scheduled for baseline = e2d7b4c and contender = 63386d1. 63386d1 is a master commit associated with this PR. Results will be available as each benchmark for each run completes.
Conbench compare runs links:
[Skipped ⚠️ Benchmarking of arrow-datafusion-commits is not supported on ec2-t3-xlarge-us-east-2] ec2-t3-xlarge-us-east-2
[Skipped ⚠️ Benchmarking of arrow-datafusion-commits is not supported on test-mac-arm] test-mac-arm
[Skipped ⚠️ Benchmarking of arrow-datafusion-commits is not supported on ursa-i9-9960x] ursa-i9-9960x
[Skipped ⚠️ Benchmarking of arrow-datafusion-commits is not supported on ursa-thinkcentre-m75q] ursa-thinkcentre-m75q
Buildkite builds:
Supported benchmarks:
ec2-t3-xlarge-us-east-2: Supported benchmark langs: Python, R. Runs only benchmarks with cloud = True
test-mac-arm: Supported benchmark langs: C++, Python, R
ursa-i9-9960x: Supported benchmark langs: Python, R, JavaScript
ursa-thinkcentre-m75q: Supported benchmark langs: C++, Java