Bug 964653 - (system-dialog) [Window Management] Implement System Dialog Window

(cherry picked from commit 438bcb33a71095081162e45b504139f5e61ed6dd)

Conflicts:
	apps/system/js/bootstrap.js
	apps/system/js/layout_manager.js
	apps/system/test/unit/mock_layout_manager.js
Merge pull request #16775 from ian-liu/bubble_tea/system/bug964653_systemDialog_refactor

Bug 964653 - (system-dialog) [Window Management] Implement System Dialog Window, r=@alivedise