ci: main and release branch pipelines cannot be interrupted (#12837)

Currently, all pipelines will be interrupted if a new commit is pushed
to the target branch. However, we do not want this behavior for release
branches or the `main` branch. This change will conditionally allow the
`main` and release branches to NOT be interrupted, while all other
branches will be interrupted when new commits are pushed.

Trying this out from the [GitLab
docs](https://docs.gitlab.com/ci/yaml/#workflowrulesauto_cancel).

## Testing
This is when I had this `erikayasuda/condtional-interrupt` branch as one
of the conditions (see [this
commit](f62b7a6)):
<img width="963" alt="Screenshot 2025-04-01 at 5 02 15 PM"
src="https://github.com/user-attachments/assets/9c59d7de-cab1-40a6-83ac-1eeec3fa5fb7"
/>

This is what happened when I removed it as a condition (only for `main`
and release branches):
<img width="965" alt="Screenshot 2025-04-01 at 5 16 48 PM"
src="https://github.com/user-attachments/assets/0f3fec8f-a4f6-4ded-af1b-b3bb40023192"
/>


## Checklist
- [x] PR author has checked that all the criteria below are met
- The PR description includes an overview of the change
- The PR description articulates the motivation for the change
- The change includes tests OR the PR description describes a testing
strategy
- The PR description notes risks associated with the change, if any
- Newly-added code is easy to change
- The change follows the [library release note
guidelines](https://ddtrace.readthedocs.io/en/stable/releasenotes.html)
- The change includes or references documentation updates if necessary
- Backport labels are set (if
[applicable](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting))

## Reviewer Checklist
- [ ] Reviewer has checked that all the criteria below are met 
- Title is accurate
- All changes are related to the pull request's stated goal
- Avoids breaking
[API](https://ddtrace.readthedocs.io/en/stable/versioning.html#interfaces)
changes
- Testing strategy adequately addresses listed risks
- Newly-added code is easy to change
- Release note makes sense to a user of the library
- If necessary, author has acknowledged and discussed the performance
implications of this PR as reported in the benchmarks PR comment
- Backport labels are set in a manner that is consistent with the
[release branch maintenance
policy](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting)

Author: erikayasuda

.gitlab-ci.yml

@@ -13,6 +13,21 @@ variables:
 default:
   interruptible: true
 
+workflow:
+  auto_cancel:
+    on_new_commit: interruptible
+    on_job_failure: all
+  rules:
+    - if: $CI_COMMIT_BRANCH == 'main'
+      auto_cancel:
+        on_new_commit: none
+        on_job_failure: none
+    - if: $CI_COMMIT_BRANCH =~ /^[0-9]+\.[0-9]+$/
+      auto_cancel:
+        on_new_commit: none
+        on_job_failure: none
+    - when: always
+
 include:
   - remote: https://gitlab-templates.ddbuild.io/libdatadog/include/one-pipeline.yml
   - local: ".gitlab/services.yml" # Include early so others can use the definitions