Introduce IInputMethodManager.StartInputParams

IInputMethod#startInput() is a hot-spot where we keep adding new
parameters recently.  Introducing a dedicated parameter object would
allow us to add further parameters with fewer lines of changes.

This CL also renames

  InputMethod#dispatchStartInputWithToken

to

  InputMethod#dispatchStartInput

for consistency.

This is a mechanical refactoring. There should be no developer
observable behavior change.

Bug: 234882948
Test: presubmit
Change-Id: I4a6af9a47db04335921a7d14efe91bfeff25c56d