Clarify userId in IMMS#createInputContentUriToken()

As a preparation make IMMS#mCurEditorInfo per-user, this CL attempts
to clarify what parts of IMMS#createInputContentUriToken() is already
multi-user aware and what parts are not.

While this CL adds one early-exit case, the observable end result
remains to be the same (except for logcat message now becomes
"Ignoring createInputContentUriToken due to user ID mismatch").

Bug: 305849394
Bug: 341558132
Test: presubmit
Flag: EXEMPT refactor
Change-Id: Ie090e09c9dcf8c63cf711cb753e6a2686faccd48