Reimplement the components GIDHTTPFetcher #319
Description
Implement the class GIDHTTPFetcher fetches data from an URL endpoint.
GIDSignIn uses this class to revoke granted scopes. GIDProfileDataFetcher uses this class to fetch profile data.
We need this class to encapsulate GTMSessionFetcherServiceProtocol and GTMSessionFetcher so other classes don't need to mock these low level classes in their tests.