GitHub: Automatic branch protection from repository rules

[lszomoru]

• Switch to using GraphQL instead of REST
• Rework the authentication flow to be more subtle
• Enable feature by default

[joaomoreno]

Currently GitHub still hasn't rolled out contributor access to the ruleset API, waiting of them to roll that out.

Next steps before enabling by default:

• Have the branch protection detection use silent: true so users aren't shown a badge
• Detect failed pushes and drive users to enable the setting, maybe some "Learn More" link

[lszomoru]

Since we cannot differentiate between a failed push due to a branch protection rule and a failed push due to a repository ruleset, we will use "may" verbiage in the dialog. Apart from the "Learn More" link, we will also provide an action for the user to sign in with their GitHub account.

[lszomoru]

Pushing to next milestone as we are still waiting for the API permission changes to be rolled out broadly.

[lszomoru]

Feature has been enabled by default. If users are signed in with their GitHub identities and are using repository rulesets we will pull that information and we will display branch protection affordances in the UI (status bar, commit action button).

[lszomoru]

Verification steps:

1. Sign out from your GitHub account in VS Code
2. Start VS Code with all the extension disabled (you can use a profile for this)
3. Open a folder/workspace that contains a git repository hosted on GitHub (ex: microsoft/vscode)
   • Confirm that the "Account" icon in the sidebar does not show a badge asking for authentication