[NTUSER][IMM32] Create the default IME window! (retry) (#4463)

[NTUSER][IMM32] Create the default IME window! (retry) (#4463)

The default IME window has to be created for each top-level window in specific condition. It is needed for implementing Japanese input.
- Add IntFocusSetInputContext helper function.
- Call IntFocusSetInputContext after sending WM_KILLFOCUS message.
- Add IntWantImeWindow, co_IntCreateDefaultImeWindow, and IntDestroyOwnedWindows helper functions.
- Create the default IME window (spwndDefaultIme) for the specified window at IntCreateWindow.
- Fix Imm32InternalLockIMC function.
CORE-11700