Add support for global 'g' flag on regexp_matches

[marregui]

This friendly guy ignores global setting when used in the context of scalar function regexp-matches.

Postgres:

select regexp_matches('#abc #def #ghi', '(#[^\s]*)', 'g');
 regexp_matches
----------------
 {#abc}
 {#def}
 {#ghi}
(3 rows)

CrateDB:

select regexp_matches('#abc #def #ghi', '(#[^\s]*)', 'g');
 ['#abc']
----------
 {"#abc"}
(1 row)

Use case:
https://community.crate.io/t/regexp-matches-with-global-flag-returns-wrong-data/232/2

[seut]

This is a documented behaviour as CrateDB uses Lucene Regular Expressions on regexp_matches. See https://crate.io/docs/crate/reference/en/latest/general/builtins/scalar.html#regular-expression-functions and https://crate.io/docs/crate/reference/en/latest/general/builtins/scalar.html#flags.