CI pipeline improvements (more label control)

A few tweaks in anticipation to the policy changes:

https://infra.apache.org/github-actions-policy.html

 - more jobs are now opt-in and can be activated with labels
   (enterprise, db, javafx, profiler, versioning, web...)
 - moved web related steps into the webcommon job to shrink ide job
 - matrix got further reduced for runs outside of PRs
 - combine some jobs into single build-system / misc job
 - fail CI if PR is not labeled