Run system tests on all platforms on MR that touches system tests

Not doing this has lead to breakage caused by different dnspython
versions on different platforms only discovered in full nightly
pipelines.

Add a triggering rule for MRs changing code in bin/test/system.
Apply this rule to all nightly-only system test jobs.

(cherry picked from commit 8c050fe15c)

.gitlab-ci.yml

@@ -270,6 +270,11 @@ stages:
     changes:
       - '**/*.py'
 
+.rule_mr_system_tests: &rule_mr_system_tests
+  - if: '$CI_MERGE_REQUEST_DIFF_BASE_SHA != null'
+    changes:
+      - 'bin/tests/system/**'
+
 .rule_mr_manual: &rule_mr_manual
   - if: '$CI_MERGE_REQUEST_DIFF_BASE_SHA != null'
     when: manual  # only run on MR if requested
@@ -327,6 +332,12 @@ stages:
     - *rule_tag
     - *rule_source_other_than_mr
 
+.extra-system-tests-triggering-rules: &extra_system_tests_triggering_rules
+  rules:
+    - *rule_tag
+    - *rule_source_other_than_mr
+    - *rule_mr_system_tests
+
 .precheck: &precheck_job
   <<: *default_triggering_rules
   <<: *base_image
@@ -988,7 +999,7 @@ gcc:almalinux8:amd64:
 system:gcc:almalinux8:amd64:
   <<: *almalinux_8_amd64_image
   <<: *system_test_job
-  <<: *api_pipelines_schedules_tags_triggers_web_triggering_rules
+  <<: *extra_system_tests_triggering_rules
   needs:
     - job: gcc:almalinux8:amd64
       artifacts: true
@@ -1191,7 +1202,7 @@ gcc:sid:amd64:
 system:gcc:sid:amd64:
   <<: *debian_sid_amd64_image
   <<: *system_test_job
-  <<: *api_pipelines_schedules_tags_triggers_web_triggering_rules
+  <<: *extra_system_tests_triggering_rules
   needs:
     - job: gcc:sid:amd64
       artifacts: true
@@ -1320,7 +1331,7 @@ gcc:jammy:amd64:
 system:gcc:jammy:amd64:
   <<: *ubuntu_jammy_amd64_image
   <<: *system_test_job
-  <<: *api_pipelines_schedules_tags_triggers_web_triggering_rules
+  <<: *extra_system_tests_triggering_rules
   needs:
     - job: gcc:jammy:amd64
       artifacts: true
@@ -1396,7 +1407,7 @@ clang:asan:
 system:clang:asan:
   <<: *base_image
   <<: *system_test_job
-  <<: *api_pipelines_schedules_tags_triggers_web_triggering_rules
+  <<: *extra_system_tests_triggering_rules
   needs:
     - job: clang:asan
       artifacts: true
@@ -1427,7 +1438,7 @@ system:gcc:tsan:
     TSAN_OPTIONS: "${TSAN_OPTIONS_FEDORA}"
   <<: *tsan_fedora_42_amd64_image
   <<: *system_test_tsan_job
-  <<: *api_pipelines_schedules_tags_triggers_web_triggering_rules
+  <<: *extra_system_tests_triggering_rules
   needs:
     - job: gcc:tsan
       artifacts: true
@@ -1513,7 +1524,7 @@ clang:trixie:amd64:
 system:clang:trixie:amd64:
   <<: *debian_trixie_amd64_image
   <<: *system_test_job
-  <<: *api_pipelines_schedules_tags_triggers_web_triggering_rules
+  <<: *extra_system_tests_triggering_rules
   needs:
     - job: clang:trixie:amd64
       artifacts: true
@@ -1535,7 +1546,7 @@ clang:freebsd13:amd64:
 system:clang:freebsd13:amd64:
   <<: *system_test_job
   <<: *freebsd_autoscaler_13_amd64
-  <<: *api_pipelines_schedules_tags_triggers_web_triggering_rules
+  <<: *extra_system_tests_triggering_rules
   needs:
     - job: clang:freebsd13:amd64
       artifacts: true