Replace deprecated only/except with rules in .gitlab-ci.yml

The keyword rules allows more flexible and complex conditions when
deciding whether to create the job and also makes it possible run tweak
variables or job properties depending on arbitraty rules. Since it's
not possible to combine only/except and rules together, replace all
uses of only/except to avoid any potential future issues.

(cherry picked from commit 29fd756408)

.gitlab-ci.yml

@@ -221,31 +221,18 @@ stages:
 ### Job Templates
 
 .api-pipelines-schedules-tags-triggers-web-triggering-rules: &api_pipelines_schedules_tags_triggers_web_triggering_rules
-  only:
-    - api
-    - pipelines
-    - schedules
-    - tags
-    - triggers
-    - web
+  rules:
+    - if: '$CI_PIPELINE_SOURCE =~ /^(api|pipeline|schedule|trigger|web)$/'
+    - if: '$CI_COMMIT_TAG != null'
 
 .api-pipelines-schedules-triggers-web-triggering-rules: &api_pipelines_schedules_triggers_web_triggering_rules
-  only:
-    - api
-    - pipelines
-    - schedules
-    - triggers
-    - web
+  rules:
+    - if: '$CI_PIPELINE_SOURCE =~ /^(api|pipeline|schedule|trigger|web)$/'
 
 .default-triggering-rules: &default_triggering_rules
-  only:
-    - api
-    - merge_requests
-    - pipelines
-    - schedules
-    - tags
-    - triggers
-    - web
+  rules:
+    - if: '$CI_PIPELINE_SOURCE =~ /^(api|merge_request_event|pipeline|schedule|trigger|web)$/'
+    - if: '$CI_COMMIT_TAG != null'
 
 .precheck: &precheck_job
   <<: *default_triggering_rules
@@ -647,9 +634,8 @@ danger:
   script:
     - pip install git+https://gitlab.isc.org/isc-projects/hazard.git
     - hazard
-  only:
-    refs:
-      - merge_requests
+  rules:
+    - if: '$CI_PIPELINE_SOURCE == "merge_request_event"'
 
 checkbashisms:
   <<: *precheck_job
@@ -1442,8 +1428,8 @@ release:
       artifacts: true
     - job: docs:pdf
       artifacts: true
-  only:
-    - tags
+  rules:
+    - if: '$CI_COMMIT_TAG != null'
   artifacts:
     paths:
       - "*-release"
@@ -1486,8 +1472,8 @@ sign:
   needs:
     - job: release
       artifacts: true
-  only:
-    - tags
+  rules:
+    - if: '$CI_COMMIT_TAG != null'
   when: manual
   allow_failure: false
 
@@ -1539,10 +1525,8 @@ coverity:
       - cov-int.tar.gz
     expire_in: "1 week"
     when: on_failure
-  only:
-    variables:
-      - $COVERITY_SCAN_PROJECT_NAME
-      - $COVERITY_SCAN_TOKEN
+  rules:
+    - if: '$COVERITY_SCAN_PROJECT_NAME != null && $COVERITY_SCAN_TOKEN != null'
 
 # Respdiff tests
 
@@ -1717,9 +1701,8 @@ pairwise:
       - pairwise-model.txt
       - pairwise-output.*.txt
     when: on_failure
-  only:
-    variables:
-      - $PAIRWISE_TESTING
+  rules:
+    - if: '$PAIRWISE_TESTING != null'
 
 .post_merge_template: &post_merge
   <<: *base_image