Wrong tags when adding multiple Rocks to OCI Factory

[lucabello]

There's a bug in our CI workflow that opens a PR to OCI Factory.

As you can see in this file (produced by our CI), multiple images are assigned the major 10-22.04 tag, which is obviously wrong (only 10.3.3 should have it, not 10.3.1).

The way we decide what to tag with major.minor and major is based on checking against the list of already-existing tags. However, this means that if we now add 11.0, 11.1, and 11.2 in the same PR, they will all be tagged as 11, which is wrong.

The CI needs to be modified to not only check against already-existing tags, but on the union of that and the tags being added/modified by the PR itself.