3632 set ci runs on master and enable integration test on android alarm manager (cla: yes, p: android_alarm_manager)

3633 Make executor an instance property (cla: yes, p: shared_preferences, platform-android, waiting for tree to go green)

3634 Fix Cirrus script for firebase testlab tests (cla: yes)

3635 [image_picker_for_web] Bump version for NNBD stable (cla: yes, p: image_picker, platform-web, waiting for tree to go green)

3636 [in_app_purchase] migrate playing billing library to v3 (cla: yes, p: in_app_purchase, platform-android, waiting for tree to go green)

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