[C++] Add regex count kernel

[asfimport]

Returns the number of times the regular expression pattern occurs in the string, like len(re.findall(...)) in Python and regexp_count() in some SQL dialects

Reporter: Ian Cook / @ianmcook
Assignee: David Li / @lidavidm

Related issues:

• [C++] String algorithm library for StringArray/BinaryArray (is a child of)
• [C++] Add regex string match kernel (relates to)
• [C++] Add substring count kernel (relates to)
• [R] bindings for str_count (is depended upon by)

PRs and other links:

• GitHub Pull Request #10471

_{Note: This issue was originally created as ARROW-12952. Please see the migration documentation for further details.}

[asfimport]

David Li / @lidavidm:
Issue resolved by pull request 10471
#10471