Add pull request message action that runs full tests

[folmos-at-orange]

Description

Currently we are running the full tests manually for each pull request. An action that reacts to a formatted message ease the launch of the full tests and leave a trace.

Questions/Ideas

• We should make sure that only members of the project can trigger the full-tests
• Is there any way to easily add the results to the PR timeline?
• Github event issue_comment:
  • https://docs.github.com/en/actions/using-workflows/events-that-trigger-workflows#issue_comment
  • https://docs.github.com/en/webhooks/webhook-events-and-payloads#issue_comment
• Action to implement commands: https://github.com/marketplace/actions/slash-commands