Reject pseudo userId in IMM#get*InputMethodList()

As a preparation before removing the dependency on ImfLock.class from
IME query APIs defined in InputMethodManager, this CL aims to clarify
that pseudo userIds (e.g. UserHandle#USER_ALL) have never been
supported in these APIs.

Note that this refinement should be invisible to app developers, who
cannot directly pass the userId to the underlying IPC methods such as

  IInputMethodManager#getCurrentInputMethodInfoAsUser().

Bug: 354323416
Test: presubmit
Flag: EXEMPT refactor
Change-Id: I93e6a6ba80cfe393b2d39ea03a5d7f97c091aed3