Fix 2402303: Split Keyboard widget from LatinIME into reusable PasswordEntryKeyboardView

- Added new PasswordEntryKeyboardView to internal/widgets.  Widget supports:
	- alpha mode with symbols (latin-1 only).
	- a numeric keyboard
	- IME emulation that applies keyboard input to arbitrary top-level view widget.
- Added new transparent assets to framework resources.
- Modified Keyguard and Keyguard layouts to use new PasswordEntryKeyboardView.