Make AutofillSuggestionsController per-user

This CL makes AutofillSuggestionsController per user instance by
making it be owned by InputMethodBindingController, which is already
instantiated for each user.

By doing InputMethodManagerService does not need to work as a
trampoline between AutofillSuggestionsController and
InputMethodBindingController.

While this is not a pure mechanical change, if there was any
observable behavior change it would be considered to be a semantic bug
that needs to be addressed sooner or later. So far existing end-to-end
tests have been passing successfully.

Test: presubmit
Fix: 339358344
Change-Id: I23125b27e7eb7d096dcb8e6fc10581b106cb6329