Enable conflict resolution in auto-generated uplifts

[wknapik]

Currently, if there are conflicts, script/uplift.py will just fail, forcing the developer to perform the entire uplift process manually.

I see 480 hits for [ERROR] cherry-pick failed for branch in the uplift channel.

We could improve this by doing everything that can be done automatically and then letting the developer resolve the conflicts.

This could be done by opening the code in some web IDE and letting the uplift requester resolve the conflicts there and create the uplift PR including the resolutions.

Another, simpler option would be to just commit the files including unresolved conflicts, create the PR(s) with a label indicating that the conflicts are there and CI shouldn't run, and let the developer check the branch out locally, resolve conflicts and push. The fix could be easily detected to remove the label via a GitHub action.

cc @bsclifton

[wknapik]

Related #38259