Deprecate str_begins in favor of stringr::str_starts

[aseagram]

Deprecate (soft/hard) str_begins in favor of stringr::str_starts function; will require updated in related packages.

[dholstius]

This is a great issue to get hands dirty editing our codebase!

@arihusain Let’s chat on Teams about the best way to handle this (are you comfortable branching, editing, and then sending a pull request)?

It’s not a critical issue, but is a good test/exercise of protocol precisely because it’s simple. And it’s a pattern that will come up again and again.