[C++] String capitalize kernel

[asfimport]

Capitalizes the first character in the string, like Python str.capitalize() 

Reporter: Ian Cook / @ianmcook
Assignee: Eduardo Ponce / @edponce

Related issues:

• [C++] String algorithm library for StringArray/BinaryArray (is a child of)
• [C++] String title case kernel (relates to)
• [C++] String swap case kernel (is related to)
• [R] Bindings for stringr::str_to_sentence (is depended upon by)

PRs and other links:

• GitHub Pull Request #10857

_{Note: This issue was originally created as ARROW-12944. Please see the migration documentation for further details.}

[asfimport]

Antoine Pitrou / @pitrou:
Issue resolved by pull request 10857
#10857