feat: support flags 'c' & 'i' for regexp_match(es)

[xxchan]

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What's changed and what's your intention?

Also fix #7130: panic when pattern is NULL

Checklist

• I have written necessary rustdoc comments
• I have added necessary unit tests and integration tests
• All checks passed in ./risedev check (or alias, ./risedev c)

Documentation

If your pull request contains user-facing changes, please specify the types of the changes, and create a release note. Otherwise, please feel free to remove this section.

Types of user-facing changes

• SQL commands, functions, and operators

Release note

Support flags 'c' & 'i' for regexp_match(es)

Refer to a related PR or issue link (optional)

#4545

[codecov]

Codecov Report

Merging #7135 (eed41bc) into main (24b6278) will decrease coverage by 0.03%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##             main    #7135      +/-   ##
==========================================
- Coverage   73.18%   73.14%   -0.04%     
==========================================
  Files        1052     1052              
  Lines      167502   167600      +98     
==========================================
+ Hits       122583   122592       +9     
- Misses      44919    45008      +89     

Flag	Coverage Δ
rust	73.14% <0.00%> (-0.04%)	⬇️

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

Impacted Files	Coverage Δ
src/expr/src/expr/expr_regexp.rs	0.00% <0.00%> (ø)
src/expr/src/expr/mod.rs	46.93% <ø> (ø)
src/expr/src/table_function/regexp_matches.rs	0.00% <0.00%> (ø)
src/frontend/src/expr/table_function.rs	39.61% <0.00%> (-3.66%)	⬇️
src/frontend/src/expr/type_inference/func.rs	88.26% <0.00%> (-3.12%)	⬇️
src/meta/src/hummock/mock_hummock_meta_client.rs	64.73% <0.00%> (-1.06%)	⬇️
src/storage/src/hummock/compactor/mod.rs	83.10% <0.00%> (-0.16%)	⬇️
src/meta/src/hummock/manager/mod.rs	79.33% <0.00%> (-0.06%)	⬇️
src/common/src/cache.rs	97.54% <0.00%> (+0.22%)	⬆️
... and 1 more

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[mergify]

Hey @xxchan, this pull request failed to merge and has been dequeued from the merge train. If you believe your PR failed in the merge train because of a flaky test, requeue it by clicking "Update branch" or pushing an empty commit with git commit --allow-empty -m "rerun" && git push.