Make isStylusHwAvailable() user-aware

IMM#isStylusHandwritingAvailable() should return result for current
user.
Also introduce internal API method isStylusHandwritingAvailable(int
userId) to query for other users when TextView#setTextOperationUser()
uses a non-current user.

Bug: 236318991
Bug: 237439688
Bug: 237418160
Test: atest StylusHandwritingTest

Change-Id: Ie5681eba3b0f1757f90377bddce9f731d4c32097