Version-gate IME show/hide async nature

Apps targeting older version may mis-use return type of
InputMethodManager#show/hideSoftInput to interpret result fo request
rather than relying on ResultReceiver.
In order to avoid breaking apps, this change version gates async nature
of those methods.

Fix: 352594277
Bug: 293640003
Test: atest CtsInputMethodTestCases
Flag: compatchange_for_zerojankproxy

Change-Id: I6b8787a2ada0b4a60e6b448b674d05e172e594a7