[FEATURE] Add new CI workflow for PRs to run tests on base branch.

[Yury-Fridlyand]

A situation might happen when a good PRs¹ was merged² into a base branch cause a failure after merge.
This happened recently with #1166.

Existing PR CI workflows run on top of the feature branch only. Merging PR cause a merge commit which triggers another CI which might fail, but it doesn't block the PR, because it is already merged... Furthermore, detect such failures is much more difficult in tons of GHA notifications.

The feature I request is to add a new CI workflow which will run in each PR and test proposed changes on base branch.

1. Workflow would be like:

git checkout <base branch>
git merge <pr branch>
./gradlew ...

2. Workflow could run simplified test suite (e.g. integration tests only).
3. Workflow should run on every change in base or feature branch, see pull_request_target

Footnotes

1. All CI passed on feature branches ↩

2. Without any conflicts ↩

[YANG-DB]

Hi
Totally agree - I also believe that the more complex system tests which call external resources like Prometheus should not be part of these acceptance tests but run after ...