Move from Drone to GitHub Actions

[susnux]

• We then can reuse Drone workers more flexible as GitHub runners for other tasks
• No need to maintain two different CI systems
• Ability to restart failed CI processes without Drone admin rights

Progress

• Move all unit tests
  • chore(tests): Run all unit tests on GitHub instead of Drone #41003
• Move all integration tests
  • fix(CI): Add missing generic files_external tests #44191
  • Move integration tests to github actions #41139
  • WebDav chore: Migrate WebDAV files_external test from Drone to GitHub #43220
  • Samba chore: Migrate samba files_external test from drone to github #43516
• Move checkers chore(CI): Migrate autocheckers from Drone to GitHub #43514
• Move Litmus / CalDAV testsuite
• Move acceptance tests (best case: use Cypress)
  • Login tests: chore(tests): Migrate login acceptance tests from behat to Cypress #41033
  • Access levels: chore(cypress): Migrate access-level tests from Behat to Cypress #41137
  • Contacts menu: chore(cypress): Migrate header contacts menu tests from Behat to Cypress #41190
  • Apps: chore(cypress): Migrate apps acceptance tests to Cypress #41303

We should prepare all of them and move them together so we can reuse the Drone workers quickly and reduce Drone to 3-5 workers for stable branches and Talk.

cc @skjnldsv @nickvergessen

[nickvergessen]

Talk migrated away already for master and stable27, so only using it for older stable branches

[nickvergessen]

That being said, it would be helpful to execute that before the branch off, or backport it, so any recent fixing isn't cloncking legacy CI immediately

[susnux]

Samba seems to be a bit more complex, but I will look into that one so we can finalize this :)