Correctly propagate userId in IMMS#setInputMethod{,AndSubtype}

With this CL the following two mehtods no longer hard code
IMMS#mCurrentUserId.

 * InputMethodManagerService#setInputMethod
 * InputMethodManagerService#setInputMethodAndSubtype

The observable behavior should remain to be the same for single user
mode.

Bug: 350386877
Test: presubmit
Flag: android.view.inputmethod.concurrent_input_methods
Change-Id: Ia8657d21d84c138b7776b3aa3fa480b4314f4d42