feat: move to marking test branches

[rnetser]

Instead of branching in the repo, tests can now be:

• marked as "upsteam", for upstream-only features
• marked as "odh", for mistream features
• marked with rhoai version on which they were developed, e.g pytest.mark.rhoai_2_16; only tests which meet the installed product version will be selected.

[github-actions]

The following are automatically added/executed:

• PR size label.
• Run pre-commit
• Run tox
• Add PR author as the PR assignee

Available user actions:

• To mark a PR as WIP, add /wip in a comment. To remove it from the PR comment /wip cancel to the PR.
• To block merging of a PR, add /hold in a comment. To un-block merging of PR comment /hold cancel.
• To mark a PR as approved, add /lgtm in a comment. To remove, add /lgtm cancel.
  lgtm label removed on each new commit push.
• To mark PR as verified comment /verified to the PR, to un-verify comment /verified cancel to the PR.
  verified label removed on each new commit push.
• To Cherry-pick a merged PR /cherry-pick <target_branch_name> to the PR. If <target_branch_name> is valid,
  and the current PR is merged, a cherry-picked PR would be created and linked to the current PR.

Supported labels

{'/lgtm', '/wip', '/hold', '/verified'}

[lugi0]

this looks ok to me, but as far as I can see we're only filtering tests based on the version marker; how do we want to handle the midstream/upstream markers?

[dbasunag]

How would we handle when a feature behavior changes between releases and when test step changes between releases?

[rnetser]

how about adding the option to add an indicator like
up_to_rhoai_2_16 and there will be another test with the new functionality which will have rhoai_2_17 ?

[dbasunag]

This would add duplicate tests and the repository can potentially get messy and hard to maintain. I don't like this idea.

[rnetser]

addressed in #231