Make new Autofill API concretes, so they don't break support library.

Test: cts-tradefed run commandAndExit cts-dev -m CtsAutoFillServiceTestCases -t android.autofillservice.cts.LoginActivityTest#testNewTextAttributes
Test: m update-api

Bug: 38323227

Change-Id: Idafb157fe9b3e96661d58923d361ea07ff2c6d40