chore: Do not use gitlab merge request pipelines

## Summary
If we define pipelines to trigger on merge requests,
they will take precedence over branch pipelines,
which is currently the way our old pipelines are still
triggered. This means that we can have a merge request
with green pipelines, but actually the external pipelines failed.
Therefore, we need to only rely on branch pipelines,
to ensure that we don't ignore the results from
external pipelines.

More information here:
- https://forum.gitlab.com/t/merge-request-considering-merge-request-pipelines-instead-of-branch-pipelines/111248/2
- https://docs.gitlab.com/17.6/ci/jobs/job_rules/#run-jobs-only-in-specific-pipeline-types

.gitlab-ci.yml

@@ -20,15 +20,30 @@ default:
         exit 0
       fi
 
+## A set of predefined rules to use on the different jobs
+.default_rules:
+  # Rules to run the job only on the master branch
+  run_on_master:
+    - if: $CI_COMMIT_BRANCH == $CI_DEFAULT_BRANCH
+      when: always
+    - when: never
+  # Rules to run the job only on branches that are not master. This is needed because for now
+  # we need to keep a similar behavior due to the integration with teamcity, which requires us
+  # to not trigger pipelines on tags and/or merge requests.
+  run_on_branch:
+    - if: $CI_COMMIT_TAG
+      when: never
+    - if: $CI_PIPELINE_SOURCE != "merge_request_event" && $CI_COMMIT_BRANCH != $CI_DEFAULT_BRANCH
+      when: always
+    - when: never
+
 # -----------------------------------------------
 # Stage 1: Build on every PR
 # -----------------------------------------------
 build_cloudflared_macos: &build
   stage: build
   rules:
-    - if: $CI_PIPELINE_SOURCE == "merge_request_event" && $CI_COMMIT_BRANCH != "master"
+    - !reference [.default_rules, run_on_branch]
-      when: always
-    - when: never
   tags:
     - "macstadium-${RUNNER_ARCH}"
   parallel:
@@ -55,14 +70,11 @@ build_cloudflared_macos: &build
 # -----------------------------------------------
 build_and_sign_cloudflared_macos:
   <<: *build
-  extends: .check_tag
   rules:
-    - if: $CI_COMMIT_BRANCH == "master"
+    - !reference [.default_rules, run_on_master]
-      when: always
-    - when: never
   secrets:
     APPLE_DEV_CA_CERT:
-      vault: gitlab/cloudflare/tun/cloudflared/_branch/master/apple_dev_ca_cert/data@kv
+      vault: gitlab/cloudflare/tun/cloudflared/_branch/master/apple_dev_ca_cert_v2/data@kv
       file: false
     CFD_CODE_SIGN_CERT:
       vault: gitlab/cloudflare/tun/cloudflared/_branch/master/cfd_code_sign_cert_v2/data@kv
@@ -93,9 +105,7 @@ release_cloudflared_macos_to_github:
   dependencies:
     - build_and_sign_cloudflared_macos
   rules:
-    - if: $CI_COMMIT_BRANCH == "master"
+    - !reference [.default_rules, run_on_master]
-      when: always
-    - when: never
   cache:
     paths:
       - .cache/pip