make sign-out / sign-in possible with multiple accounts

Many developers have multiple Git-Accounts:

- work
- university
- private accounts
- public (and non-work, non-university related) accounts

(For simplicity let us just make the unrealistic assumption that all of these git accounts are on GitHub.)

The GitHub Pull Request extension in MS VSCode respects these. (I guess it just observes what the local .git/config is.)


But the GitHub Actions extension in VSCode does not.
There is not even the option to "sign in/out" and manually select an account. (I think you do it once and cannot change it thereafter.)


## Proposed solution ##

I would like to see e.g.

1. a Command Palette menu option to sign in/out for the GitHub Actions extension


or the Actions and PR extensions should have synchronised settings
(vis-a-vis current account for current workspace)

2. the ability to possible set Git[Hub] Account at the (VSCode) profile level

3. possibly a way to do select accounts via VSCode's (local or global) **settings.json**

Start by comparing the GitHub Actions and GitHub Pull Request extension sign-in behavior, including the local .git/config and VS Code Command Palette. Review how VS Code profiles and local or global settings.json could represent an account, then define a consistent sign-in/sign-out flow with workspace-level account selection as the completion criterion.

Written by the indexing model from the issue text.