Automate regular Maven release deployment

[lauraharker]

We want to start regularly pushing Maven releases. I'll work with @jDramaix and @12wrigja on automating this process.

Possibly related issues: #4215 , #4168, #4208, #4161

[lauraharker]

The general plan is to:

• use the contents of https://github.com/google/closure-compiler/blob/master/.github/piper-cut-cl.json to automatically tag commits that correspond to a Google internal release commit
• regularly (at least once a month, maybe weekly) run a workflow to take the latest tagged commit & upload it to Maven

The goal of https://github.com/google/closure-compiler/blob/master/.github/piper-cut-cl.json is so that there's some signal that a given commit is good & safe to cut a release at, since we do a lot of internal testing already before releasing.

We also currently do internal releases at least 1x per week, sometimes 4x.