* [google_sign_in_web] Migrate to GIS SDK.

* include_granted_scopes in requestScopes call.

* Remove the old JS-interop layer.

* Introduce a mockable GisSdkClient for tests.

* Split the people utils.

* Delete tests for the old code.

* Add some tests for the new code.

* More utils_test.dart

* Make jsifyAs reusable.

* Ignore the tester in utils_test.dart

* Make Clients overridable, and some renaming.

* Test people.dart

* Make autoDetectedClientId more testable.

* Add mockito.

* Comment about where to better split the code so GisSdkClient is testable too.

* Add google_sign_in_web_test.dart (and its mocks)

* dart format

* Log only in debug.

* Sync min sdk with package gis_web

* Add migration notes to the README.

* When the user is known upon signIn, remove friction.

* Do not ask for user selection again in the authorization popup
* Pass the email of the known user as a hint to the signIn method

* Address PR comments / checks.

* Update migration guide after comments from testers.

* Update README.md

* Remove package:jose from tests.

* Rename to Vincent Adultman

* _isJsSdkLoaded -> _jsSdkLoadedFuture

* Remove idToken comment.

* Link issue to split mocking better.

* Remove dependency in package:jwt_decoder

* Remove unneeded cast call.