Move build support into lkdev package

[mdekstrand]

This moves our build support code into an lkdev package so dependencies live in pyproject.toml.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.98%. Comparing base (9daac79) to head (abeb934).
Report is 567 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #431   +/-   ##
=======================================
  Coverage   90.98%   90.98%           
=======================================
  Files          47       47           
  Lines        3207     3207           
=======================================
  Hits         2918     2918           
  Misses        289      289           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.