non-pre calver releases of builtins

[masklinn]

• because uap-core has not cut a release in a long time, the "official" release is getting long in the tooth (YaSearchBrowser UA is mis-detected as Chrome — bundled uap-core is outdated #270, Bump uap-python-builtins as it's 8 months out of date #271)
• request for official guidance has yielded no feedback yet (Plans for releases / tagging of regexes.yaml? uap-core#641)
• calendar versioning makes a lot of sense for -builtins, since there are no real semantics to the package (there is no API, except in the sense that I could add new serializations in the future — a hypothetical precompiled aho FSM for just as hypothetical a pure python prefilter cough cough Build & evaluate pure python regex filter #235 cough cough for instance — but that's for ua-parser to deal with, it should be of no concern to end users)

The plan here would be:

• keep the current monthly cron, but instead of generating a version based on -core tags use the release date (year.month)
  • no need to increment the epoch since calver naturally sorts later than semver
• add the source uap-core commit to either the package's __init__ or a packaged data file (data / resources?)
• after checking out -core but before building the wheel
  • retrieve the latest version off of pypi (how?)
  • read out the resource file where the commit-id is located
  • compare to the current head of -core
  • if identical, bail out of releasing
• otherwise generated the code
• add the commit-id to the generated content
• and build and upload the wheel