Currently, authenticate FillResponses do not support partition and follows
the "Highlander approach" (There can be just only one), which causes the
authentication UI to show on all views.
This CL overloads FillResponse.setAuthentication() so it requires the
AutofillIds of the autofillable fields, although behind the scenes it
calls the old method - once clients use the new method, the old method
will be removed and the underlying implementation changed.
The new behavior will be tested by testFillResponseAuthJustOneField()
on LoginActivityTest, although currently it's testing the old behavior.
Test: LoginActivityTest.testFillResponseAuthJustOneField
Bug: 35707731
Bug: 36855717
Change-Id: I601f3e4776aa8763415a06d8d802901a930728d2
b3c3537566