Use AvailableVirtualKeyboardFragment for IME settings

CL[1] make InputMethodPreference support:
-. Tap to corresponding IMEs settings
-. Using switch to enable/disble IMEs

Using AvailableVirtualKeyboardFragment for
language and input settings entries and
remove unused files.

[1]: I445551e4112117aabd8d7a48f53c29b7ffd8bafd

Bug: 197705032
Test: Manually test settings keyboard flow, test video in bug
Change-Id: I4d74df7d2dda71661e3298c7070459885aa308cb