ci: use ubuntu-latest for functional tests. Improve CI caching

[wzieba]

Description

This PR:

• moves running functional tests from macOS to Ubuntu runner as KVM is now enabled on Ubuntu. The improvement is significant - from ~13m to ~5m per run
• delegates caching to gradle-build-action
• send dependencies on each push because it helps in tracking closed security alerts
• caches AVD files

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (761cf77) 57.60% compared to head (230ce39) 57.60%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #107   +/-   ##
=======================================
  Coverage   57.60%   57.60%           
=======================================
  Files          19       19           
  Lines         401      401           
  Branches       48       48           
=======================================
  Hits          231      231           
  Misses        157      157           
  Partials       13       13           

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[wzieba]

Merging without review, as this PR contains only CI changes. I'm fairly confident with them. They don't affect the production code.