Extract static analysis to a separate CI file

`static-analysis` is not rails specific and
performs various kinds of static analyses:
rubocop, haml, jest, markdown, etc.

.gitlab/ci/rails.gitlab-ci.yml

@@ -229,49 +229,6 @@ update-gitaly-binaries-cache:
     SETUP_DB: "false"
     USE_BUNDLE_INSTALL: "false"
 
-.static-analysis-base:
-  extends:
-    - .default-retry
-    - .default-before_script
-    - .static-analysis-cache
-  needs: []
-  variables:
-    SETUP_DB: "false"
-    ENABLE_SPRING: "1"
-    # Disable warnings in browserslist which can break on backports
-    # https://github.com/browserslist/browserslist/blob/a287ec6/node.js#L367-L384
-    BROWSERSLIST_IGNORE_OLD_DATA: "true"
-
-update-static-analysis-cache:
-  extends:
-    - .static-analysis-base
-    - .static-analysis-cache-push
-    - .shared:rules:update-cache
-  stage: prepare
-  script:
-    - run_timed_command "bundle exec rubocop --parallel"  # For the moment we only cache `tmp/rubocop_cache` so we don't need to run all the tasks.
-
-static-analysis:
-  extends:
-    - .static-analysis-base
-    - .static-analysis:rules:ee-and-foss
-  stage: test
-  parallel: 4
-  script:
-    - run_timed_command "retry yarn install --frozen-lockfile"
-    - scripts/static-analysis
-  artifacts:
-    expire_in: 31d
-    when: always
-    paths:
-      - tmp/feature_flags/
-
-static-analysis as-if-foss:
-  extends:
-    - static-analysis
-    - .static-analysis:rules:as-if-foss
-    - .as-if-foss
-
 rspec migration pg12:
   extends:
     - .rspec-base-pg12

.gitlab/ci/static-analysis.gitlab-ci.yml

+.static-analysis-base:
+  extends:
+    - .default-retry
+    - .default-before_script
+    - .static-analysis-cache
+  needs: []
+  variables:
+    SETUP_DB: "false"
+    ENABLE_SPRING: "1"
+    # Disable warnings in browserslist which can break on backports
+    # https://github.com/browserslist/browserslist/blob/a287ec6/node.js#L367-L384
+    BROWSERSLIST_IGNORE_OLD_DATA: "true"
+
+update-static-analysis-cache:
+  extends:
+    - .static-analysis-base
+    - .static-analysis-cache-push
+    - .shared:rules:update-cache
+  stage: prepare
+  script:
+    - run_timed_command "bundle exec rubocop --parallel"  # For the moment we only cache `tmp/rubocop_cache` so we don't need to run all the tasks.
+
+static-analysis:
+  extends:
+    - .static-analysis-base
+    - .static-analysis:rules:ee-and-foss
+  stage: test
+  parallel: 4
+  script:
+    - run_timed_command "retry yarn install --frozen-lockfile"
+    - scripts/static-analysis
+  artifacts:
+    expire_in: 31d
+    when: always
+    paths:
+      - tmp/feature_flags/
+
+static-analysis as-if-foss:
+  extends:
+    - static-analysis
+    - .static-analysis:rules:as-if-foss
+    - .as-if-foss