Move IMMS#mCurHostInputToken to AutofillSuggestionsController

This is a preparation before making AutofillSuggestionsController
per-user instance.

Apparently

  InputMethodManagerService#mCurHostInputToken,

has been used only from AutofillSuggestionsController since it was
originally introduced [1]. Such a data should live in the controller
rather than InputMethodManagerService itself.

This is a mechanical refactoring CL. There must be no observable
behavior change.

 [1]: I268b09781e5eb7c77c4912efdc8fd5d6936ada27

Bug: 339358344
Test: atest CtsAutoFillServiceTestCases
Test: atest CtsInputMethodTestCases
Change-Id: I6529f81145b1a31a3438a23eca57106093b1ae07