test(e2e): cover force policy tag selection regressions in k3s suite

Add behavioral e2e scenarios for issue #823 that run in CI on the
task-owned k3s cluster:

- force-latest: a workload on 1.0.0 must converge on the newest
  available tag (1.0.2), not an arbitrary tag from the unsorted
  registry tag list.
- force-nodowngrade: a workload on 1.0.1 with an older 1.0.0 tag
  available must remain untouched (8.1.0 -> 8.0.0 report).
- force-prerelease: a workload on 7.9.1-1-ubi8 with only older tags
  (3.0.0, 5.0.0) available must remain untouched (original cp-kafka
  report).

Seed the corresponding fixture repositories in the e2e registry.

Spec-Ref: helix-specs@f4068b83:000386_investigate