[8.14](backport #39298) Branch specific concurrency gates

[mergify]

Proposed commit message

PR #39293 introduced one concurrency queue per staging/snapshot but this slows down unnecessarily concurrent DRA builds for main and other release branches.

This commit makes the concurrency gates specific per branch.

Related issues

• https://github.com/elastic/ingest-dev/issues/3095

Logs

Example run: https://buildkite.com/elastic/beats-packaging-pipeline/builds/99#018f2ed1-88f4-4f2a-9604-e29c51eba3a3

Screenshots

First run:

Blocked second run (as expected):

---

This is an automatic backport of pull request #39298 done by [Mergify](https://mergify.com).

[dliappis]

LGTM as it's a clean automated backport

[elasticmachine]

💚 Build Succeeded

the below badges are clickable and redirect to their specific view in the CI or DOCS

Expand to view the summary

Build stats

• Duration: 15 min 43 sec

❕ Flaky test report

No test was executed to be analysed.

🤖 GitHub comments

Expand to view the GitHub comments

To re-run your PR in the CI, just comment with:

• /test : Re-trigger the build.

• /package : Generate the packages and run the E2E tests.

• /beats-tester : Run the installation tests with beats-tester.

• run elasticsearch-ci/docs : Re-trigger the docs validation. (use unformatted text in the comment!)