Try to auto-detect which remote points to github.com

**Is your feature request related to a problem? Please describe.**

The extension couldn't find GitHub repository for the git repository when both of the following conditions are met:

- git repository has two remotes
- github url is not set as `origin` remote

i.e.:

```
$ git remote -v
github https://github.com/my-org/my-repo.git (fetch)
github https://github.com/my-org/my-repo.git (push)
origin https://internal-scm.example.com/my-repo.git (fetch)
origin https://internal-scm.example.com/my-repo.git (push)
```

**Describe the solution you'd like**
Let the extension detect GitHub repository from all the remotes, not only from `origin`.

**Additional context**

AFAIK GitHub CLI supports this scenario.

Start by tracing the extension's Git remote detection entry point and identify where it assumes the GitHub URL is on origin. Exercise it with the two-remote example from the issue; done means a GitHub remote is detected even when origin points to the internal SCM, without breaking the existing origin case.

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