feat: move to using pub workspaces

[eseidel]

This doesn't include ui due to: dart-lang/sdk#60888

This won't work yet without fixing the docker files. They will need to
copy the root level pubspec.lock into the docker image and then run
dart pub get --offline.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 78.10%. Comparing base (36f3cd7) to head (9eaf306).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #107   +/-   ##
=======================================
  Coverage   78.10%   78.10%           
=======================================
  Files         193      193           
  Lines        8730     8730           
=======================================
  Hits         6819     6819           
  Misses       1911     1911           

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

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.