Use GH Apps instead of a Member with a PAT

[kunaals]

Move to GH Apps: Use GH apps instead of a member with a PAT

Description:
To auth to GitHub today Cartography uses a GH member with a PAT as a sort of service account instead of using GH apps. This makes it appear as if there is a member within the organization who doesn't have 2FA enabled and is generally old school. We should move to using GH apps.

[optional Relevant Links:]
https://docs.github.com/en/apps/creating-github-apps/about-creating-github-apps/deciding-when-to-build-a-github-app#choosing-between-a-github-app-or-a-personal-access-token