Add smalljob tag to small jobs not in the quick-checks stage

Add smalljob tag to small jobs not in the quick-checks stage

Jobs using the "post_merge" and "manual_release_job_qa" anchors also
complete in less than a minute, so they now include the "smalljob" tag.

Since the "release" job is also a fast one, but without an anchor, the
"smalljob" tag is added to its definition.

The "autoconf_job" definion also includes the tag and it is kept in its
own stage.

(cherry picked from commit e9f2b7944e6d9ad3e93357046828e92d61e15108)