Cleanup CI scripts (#12205)

* Delete unused scripts

- gen_tags.sh: not the right file, produce garbage even if path is fixed
- premoderator.sh: not used since ef6d24a49 (CI require a 'lgtm' or
  'ok-to-test' labels to pass (#11251), 2024-05-31)
- gitlab-branch-cleanup: unused AFAICT

* CI: inline molecule logs

Single use site -> less indirection makes it easier to read.

.gitlab-ci/molecule.yml

@@ -16,7 +16,10 @@
   script:
   - ./tests/scripts/molecule_run.sh
   after_script:
-  - ./tests/scripts/molecule_logs.sh
+  - rm -fr molecule_logs
+  - mkdir -p molecule_logs
+  - find ~/.cache/molecule/ \( -name '*.out' -o -name '*.err' \) -type f | xargs tar -uf molecule_logs/molecule.tar
+  - gzip molecule_logs/molecule.tar
   artifacts:
     when: always
     paths: