[Epic] Testing Overhaul 2024

[dereknola]

This is an epic to track all the changes for testing in Q1 2024. Since most testing is self tested in the CI, QA for most of this is not necessary.

Unit tests

• Remove matrix in unit testing, update dependecies  #9478
• Fix K3s golang test Cache Thrashing  #9494

E2E

• Implement E2E testing in GitHub Actions #9659
• Convert Snapshotter into E2E test (completed with Enable E2E tests on GitHub Actions #9660)
• Update Install/Cgroup CI testing with newer OS #8591
• E2E: Embedded Registry test is broken #9656
• Move E2E onto newer base OS #9753
• Add E2E Split server test to PR CI #9754

Drone

• Move scripts/test-* into tests folder.  #9553
• Migrate Docker tests from Drone to GHA #10421

General Testing

• Update GitHub upload and download actions to v4 #9501
• Create ADR giving more details on all of the above Testing ADR #9562
• E2E: Add preload images subtest #8084
• Update nightly tests to run from commits on specified branches #6059