T7981: conflict check workflow using py script updated to support schedule and workflow dispatch (circinus) (backport #102)

[kumvijaya]

Change Summary

Backport from PR #102
PR Conflict Check Workflow (with py script) - Updated for Scheduled Execution

Enhanced the PR conflict checking workflow to support scheduled and manual triggers, addressing the issue where GitHub's mergeable state is unreliable immediately after commits.

The scheduled approach will help to solve the issue where immediate post-commit checks don't provide accurate merge status, ensuring comprehensive and reliable conflict detection.

Note:
Corresponding caller workflows will be added in subsequent PRs, with both schedule and workflow-dispatch triggers.

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):

Related Task(s)

https://vyos.dev/T7981

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