Add downgrade cancellation e2e tests

[henrybear327]

Part 2 of the e2e test - downgrade cancellation is called after the cluster has been partially downgraded

This PR is currently based on #19244, thus, it's put in draft mode for now.

Reference: #17976

Please read https://github.com/etcd-io/etcd/blob/main/CONTRIBUTING.md#contribution-flow.

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: henrybear327
Once this PR has been reviewed and has the lgtm label, please assign spzala for approval. For more information see the Code Review Process.

The full list of commands accepted by this bot can be found here.

Needs approval from an approver in each of these files:

• OWNERS

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 68.78%. Comparing base (7c56ef2) to head (fe607d8).
Report is 2 commits behind head on main.

Additional details and impacted files

see 20 files with indirect coverage changes

@@           Coverage Diff           @@
##             main   #19252   +/-   ##
=======================================
  Coverage   68.77%   68.78%           
=======================================
  Files         420      420           
  Lines       35649    35649           
=======================================
+ Hits        24518    24521    +3     
+ Misses       9705     9699    -6     
- Partials     1426     1429    +3     

---

Continue to review full report in Codecov by Sentry.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 7c56ef2...fe607d8. Read the comment docs.

[henrybear327]

Will continue to investigate this tomorrow