Fixed new multi-screens autofill API:

- Previous FillContexts should be shown on subsequent FillRequests.
- Client state should be properly propagated.

Test: atest MultiScreenLoginTest
Test: atest CtsAutoFillServiceTestCases # to make sure it didn't break anything

Fixes: 112051762
Bug: 113281366

Change-Id: I17de046385bd923279684d461afd24b49ad6f89a