Test: Auth provider proposed API

[vscodebot]

Testing [https://github-com/microsoft/vscode/issues/88309](Auth provider proposed api}

• anyOS
• anyOS

Complexity: 4

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The proposal for the authentication provider API currently looks like:
https://github-com/microsoft/vscode/blob/8d36d09ee78e9b2be62cba2f7f686341c062575b/src/vs/vscode.proposed.d.ts!L21-L60

This API enables two different use cases: I can write and register my own auth provider, or I can access existing auth providers and leverage them. The first part of this has been fairly well tested by work I've done for settings sync and for creating a GitHub provider. Please review this part of the API and give any feedback you have about it, but focus on testing using authentication.providers and authentication.onDid[Un]RegisterAuthenticationProvider events. A provider with id "MSA" which supplies the auth for settings sync should be available.
Please test that

• You can access this provider and call methods on it from an extension
• When you call getSessions or login, a dialog asking for user consent is shown