feat: hk-migrate-fork-pr action

[moe-ad]

@germa89 pinging you just to make you aware work on this has started. I will ping you again once I am done with the implementation or if I get stuck.

Summary of tasks completed

• Nothing much to say about the implementation, @germa89's work already provided the template.
• Just so we can avoid JS in ansys/actions, I have opted to use gh-cli instead of actions/github-script.
• Examples added to the documentation.
• Permissions required to run the action documented.

Closes #867.

[germa89]

Go for it :)

[moe-ad]

@germa89 @RobPasMue @SMoraisAnsys
I have tested some of the gh cli scripts in a hacky way locally, but to test end to end, this needs to be on the main branch.
If anything isn't looking good, I can iterate in subsequent PRs.

Edit: @RobPasMue synced with me offline and we will test this from another repo. No need for this to be merged before testing.

[moe-ad]

Tests.

• Forked PR vs Migrated PR.

List of TODOs:

• The comment added by the bot needs to make it explicit that the PR author is unable to push to the migrated PR branch but they can keep pushing to their fork.
• The git logic for committing changes in the case of auto/theirs/ours needs to be corrected.