3622 [google_sign_in_web] Ignore analyzer checks in generated files. (cla: yes, p: google_sign_in, platform-web)

3628 [google_sign_in_web] Migrate to null-safety (cla: yes, nnbd, p: google_sign_in, platform-web, waiting for tree to go green)

3637 [google_sign_in] Bump app-facing version for NNBD stable (cla: yes, p: google_sign_in)

3640 [google_sign_in] Adds support to send clientId as a parameter (cla: yes, p: google_sign_in, platform-android, platform-ios, waiting for tree to go green)

3642 [extension_google_sign_in_as_googleapis_auth] Migrate to null safety (cla: yes, p: google_sign_in)