T8218: Updated workflows for pullrequest_target policy change

[kumvijaya]

Change Summary

This PR updates pull_request_target workflows to comply with GitHub's recent policy change announced on November 7, 2025 Actions: pull_request_target and environment branch protections changes.

Background
GitHub updated how pull_request_target workflows are evaluated. Previously, these workflows were evaluated using the PR's target branch. Now, they are always evaluated using the repository's default branch (current). This means branch-filtered workflows will only trigger reliably if they exist and match on the default branch.

Changes
Updated the workflows to include all supported branches in their pull_request_target trigger:

Since pull_request_target workflows are now evaluated from the default branch, the workflow file must exist unchanged on the default branch. To support branch-specific triggering across all maintained branches (current, circinus, sagitta), the branch filters must explicitly list all branches or be removed entirely.

These changes ensure that:
Workflows trigger correctly for PRs targeting any of the three supported branches
The workflow files are evaluated from the current branch as per GitHub's new requirement

Note:
As these workflows doesn't have any branch-specific logic, no changes needed apart from this.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Code style update (formatting, renaming)
• Refactoring (no functional changes)
• Other (please describe): Policy update

Related Task(s)

https://vyos.dev/T8218

Related PR(s)

Proposed changes

How to test

Checklist:

• I have read the CONTRIBUTING document
• I have linked this PR to one or more Phabricator Task(s)
• My commit headlines contain a valid Task id
• My change requires a change to the documentation
• I have updated the documentation accordingly

[c-po]

Update Workflow to same model as used in our other repos.