Updated LoginButton events to respond to GlobalProvider

[shweaver-MSFT]

Fixes #101

PR Type

What kind of change does this PR introduce?

• Feature

What is the current behavior?

Currently, the Login/Logout-Completed events on LoginButton only fire when actually interacting with the button. This can make it difficult to use the LoginButton events reliably, since they won't fire if the GlobalProvider is updated directly.

What is the new behavior?

The new behavior allows the LoginButton to emit Login/Logout-Completed events in response to state changes in the GlobalProvider. When the GlobalProvider state changes, the LoginButton will emit those events as appropriate.

Note: The Login/Logout-Initiated events will not fire. This is because we have limited ability to understand the login flow based on the ProviderState enum values, SignedIn, SignedOut, and Loading.

PR Checklist

Please check if your PR fulfills the following requirements:

• Tested code with current supported SDKs
• Sample in sample app has been added / updated (for bug fixes / features)
  • Icon has been created (if new sample) following the Thumbnail Style Guide and templates
• Tests for the changes have been added (for bug fixes / features) (if applicable)
• Header has been added to all new source files (run build/UpdateHeaders.bat)
• Contains NO breaking changes

Other information

[ghost]

Thanks shweaver-MSFT for opening a Pull Request! The reviewers will test the PR and highlight if there is any merge conflict or changes required. If the PR is approved we will proceed to merge the pull request 🙌