Ved 809 destroy pipeline

[Akol125]

Summary

• Our continuous-disintegration pipeline in GitHub Actions previously triggered an Azure DevOps teardown pipeline to clean up PR environments. This created reliance on Azure DevOps for backend teardown tasks.

This PR migrates the teardown logic fully into GitHub Actions, changes Introduced
• Added a new GitHub Actions teardown workflow that runs on PR closure.
• Replicated teardown steps from Azure DevOps

Reviews Required

• Dev
• Test
• Tech Author
• Product Owner

Review Checklist

ℹ️ This section is to be filled in by the reviewer.

• I have reviewed the changes in this PR and they fill all or part of the acceptance criteria of the ticket, and the code is in a mergeable state.
• If there were infrastructure, operational, or build changes, I have made sure there is sufficient evidence that the changes will work.
• I have ensured the changelog has been updated by the submitter, if necessary.

[github-actions]

This branch is working on a ticket in the NHS England VED JIRA Project. Here's a handy link to the ticket:

VED-809

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud