Add swift concurrency for auth flow

[luizgustavo09]

Description

Obs: Changed logs and version will be updated on final version, not for draft

This PR adds modern async/await versions of all authentication methods while maintaining full backward compatibility with existing completion-based APIs.

New public API:

let client = try await UberAuth.login(context: context)

Key changes:

• Added async/await methods to UberAuth, AuthProviding, and NetworkProvider
• Old completion-based APIs remain functional and are marked as deprecated

Testing

• Added 18 new async/await unit tests covering full authentication flow
• Updated all mocks to support async/await
• Verified backward compatibility - existing completion-based code still works

[CLAassistant]

All committers have signed the CLA.