feat: Don't require installation id in github provider

[zachaller]

We can get the installation id via code following this: https://docs.github.com/en/apps/creating-github-apps/authenticating-with-a-github-app/authenticating-as-a-github-app-installation#using-an-installation-access-token-to-authenticate-as-an-app-installation

We should validate that this makes sense to do as well. Such as will this cause more API calls are there any downsides to doing this?

Maybe we support both modes where if an installation id is configured in secret we use it if not we programatically get it.