Bug 1067264 - Remove delay of layout/IME deactivation in built-in keyboard app as a follow-up of bug 1057898

- The need for delaying deactivation is no longer needed after bug 1057898 and bug 1067266.
- StateManager.DEACTIVATE_DELAY is removed.
- In deactivation, propogatation the triggering of setTimeout callback (of the delay), in forms of resolution of Promises, is removed. Async codes made into sync codes.
- Unit test cases regarding rapid activation after deactivation, and vice versa, are removed, since the behavior should now be guarded by Gecko.
Merge pull request #24205 from mnjul/bug_1067264_remove_blur_delay_kb_app

Bug 1067264 - Remove delay of layout/IME deactivation in built-in keyboard app as a follow-up of bug 1057898. r=timdream