Outside Collaborator support for Fine-grained PATs [GA]

### Value Prop

Users invited as collaborators on a repository will be able to mint a fine-grained PAT (Personal Access Token) that can access that repository. This ensures that open source projects and least-privilege access patterns can still use fine-grained PATs to access these repositories instead of using PATs (Classic)

### Expected Outcome

Fine-grained PATs need to support all of the same use cases as PATs (Classic), including their use against repositories where the developer isn't an organization member (or the repository is owned by a user). As more parity gaps are closed, we hope to see more developers moving away from PATs (Classic) and onto the more secure fine-grained alternative.