feat(expr): add regexp_split_to_array

[xzhseh]

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What's changed and what's your intention?

resolve #12509.

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).
• My PR contains breaking changes. (If it deprecates some features, please create a tracking issue to remove them in the future).
• All checks passed in ./risedev check (or alias, ./risedev c)
• My PR changes performance-critical code. (Please run macro/micro-benchmarks and show the results.)

• My PR contains critical fixes that are necessary to be merged into the latest release. (Please check out the details)

Documentation

• My PR needs documentation updates. (Please use the Release note section below to summarize the impact on users)

Release note

Support regexp_split_to_array function

[codecov]

Codecov Report

Merging #12844 (e1f49fc) into main (fcc2469) will decrease coverage by 0.02%.
The diff coverage is 13.04%.

@@            Coverage Diff             @@
##             main   #12844      +/-   ##
==========================================
- Coverage   69.18%   69.17%   -0.02%     
==========================================
  Files        1489     1489              
  Lines      245832   245901      +69     
==========================================
+ Hits       170083   170091       +8     
- Misses      75749    75810      +61     

Flag	Coverage Δ
rust	69.17% <13.04%> (-0.02%)	⬇️

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

Files	Coverage Δ
src/frontend/src/binder/expr/function.rs	78.38% <100.00%> (+0.01%)	⬆️
src/frontend/src/expr/pure.rs	87.69% <ø> (ø)
src/expr/impl/src/scalar/regexp.rs	13.40% <11.76%> (-0.39%)	⬇️

... and 2 files with indirect coverage changes

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[TennyZhuang]

Can you enable regress tests in

risingwave/src/tests/regress/data/sql/strings.sql

Lines 235 to 261 in e24370d

	-- split string on regexp
	--@ SELECT foo, length(foo) FROM regexp_split_to_table('the quick brown fox jumps over the lazy dog', $re$\s+$re$) AS foo;
	--@ SELECT regexp_split_to_array('the quick brown fox jumps over the lazy dog', $re$\s+$re$);
	--@
	--@ SELECT foo, length(foo) FROM regexp_split_to_table('the quick brown fox jumps over the lazy dog', $re$\s*$re$) AS foo;
	--@ SELECT regexp_split_to_array('the quick brown fox jumps over the lazy dog', $re$\s*$re$);
	--@ SELECT foo, length(foo) FROM regexp_split_to_table('the quick brown fox jumps over the lazy dog', '') AS foo;
	--@ SELECT regexp_split_to_array('the quick brown fox jumps over the lazy dog', '');
	--@ -- case insensitive
	--@ SELECT foo, length(foo) FROM regexp_split_to_table('thE QUick bROWn FOx jUMPs ovEr The lazy dOG', 'e', 'i') AS foo;
	--@ SELECT regexp_split_to_array('thE QUick bROWn FOx jUMPs ovEr The lazy dOG', 'e', 'i');
	--@ -- no match of pattern
	--@ SELECT foo, length(foo) FROM regexp_split_to_table('the quick brown fox jumps over the lazy dog', 'nomatch') AS foo;
	--@ SELECT regexp_split_to_array('the quick brown fox jumps over the lazy dog', 'nomatch');
	--@ -- some corner cases
	--@ SELECT regexp_split_to_array('123456','1');
	--@ SELECT regexp_split_to_array('123456','6');
	--@ SELECT regexp_split_to_array('123456','.');
	--@ SELECT regexp_split_to_array('123456','');
	--@ SELECT regexp_split_to_array('123456','(?:)');
	--@ SELECT regexp_split_to_array('1','');
	--@ -- errors
	--@ SELECT foo, length(foo) FROM regexp_split_to_table('thE QUick bROWn FOx jUMPs ovEr The lazy dOG', 'e', 'zippy') AS foo;
	--@ SELECT regexp_split_to_array('thE QUick bROWn FOx jUMPs ovEr The lazy dOG', 'e', 'iz');
	--@ -- global option meaningless for regexp_split
	--@ SELECT foo, length(foo) FROM regexp_split_to_table('thE QUick bROWn FOx jUMPs ovEr The lazy dOG', 'e', 'g') AS foo;
	--@ SELECT regexp_split_to_array('thE QUick bROWn FOx jUMPs ovEr The lazy dOG', 'e', 'g');

? Just remove --@ here (See https://github.com/risingwavelabs/risingwave/blob/f2a3fd021059e680b35b24c63cff5f8dbe9f9d5f/src/tests/regress/README.md for details)

You can only enable tests that passed now. Not necessary to support them all.

[TennyZhuang]

🤔

SELECT regexp_split_to_array('123456','1');
2023-10-16T08:36:56.624001Z ERROR risingwave_regress_test::schedule: Diff:
  regexp_split_to_array
 -----------------------
- {"",23456}
+ {23456}
 (1 row)

2023-10-16T08:36:56.624016Z ERROR risingwave_regress_test::schedule: query input:
SELECT regexp_split_to_array('123456','6');
2023-10-16T08:36:56.624032Z ERROR risingwave_regress_test::schedule: Diff:
  regexp_split_to_array
 -----------------------
- {12345,""}
+ {12345}
 (1 row)

2023-10-16T08:36:56.624044Z ERROR risingwave_regress_test::schedule: query input:
SELECT regexp_split_to_array('123456','.');
2023-10-16T08:36:56.624064Z ERROR risingwave_regress_test::schedule: Diff:
- regexp_split_to_array
-------------------------
- {"","","","","","",""}
+ regexp_split_to_array
+-----------------------
+ {}
 (1 row)

[xzhseh]

This is due to, currently, we treat the delimiter which contains empty separated field as pure empty, but postgres treats these as empty string.
I will ensure and conform to postgres's standard for this later.