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 e9f2b7944e)

.gitlab-ci.yml

@@ -346,6 +346,8 @@ stages:
   <<: *default_triggering_rules
   <<: *base_image
   stage: autoconf
+  tags:
+    - smalljob
   script:
     - autoreconf -fi
   artifacts:
@@ -1726,6 +1728,8 @@ release:
       artifacts: true
     - job: docs:pdf
       artifacts: true
+  tags:
+    - smalljob
   rules:
     - *rule_tag
   artifacts:
@@ -1856,6 +1860,8 @@ publish:
   needs:
     - job: staging
       artifacts: false
+  tags:
+    - smalljob
 
 # Setting the FORCE_CVE_IDS environment variable to a comma-separated
 # list of CVE IDs enables overriding the autodetected ones.
@@ -2168,6 +2174,8 @@ pairwise:
   <<: *base_image
   stage: postmerge
   needs: []
+  tags:
+    - smalljob
   # post-merge processes should run even if another MR was merged while the job was running (or queued)
   interruptible: false
   variables: