Preinstall collections and fix docker push on PRs

Pushes to tag matching branch name if not on the main branch, but will use latest in the specific case of a pipeline run on mainline.

Pre-installs the three ansible-galaxy collections used in the main ansible-repo, can also be extended later.

requested review from @falk.rehse and @felix

assigned to @monsterdruide1

mentioned in commit 4d29e648

merged