Purge distros token in a separate CI job

Purge distros token in a separate CI job

The "publish" job runs on a dedicated, locked-down runner that lacks the
Python modules necessary to execute the manage_distros_token.py script.
Instead of deleting the token within the "publish" job, purge it in a
separate job that automatically runs on the "base" image after the
"publish" job succeeds.  Define "rules" for the new job so that the
token is only deleted for security releases, as it should have been
initially.

(cherry picked from commit 36411e7c84384168ab3c0e3d107be459326c1647)