Separate unit and integration tests from AutofillValueTest

1. Move integration tests to CheckoutActivityTest.
2. Make AutofillValueTest be a unit test.

Bug: 159304958
Test: atest android.autofillservice.cts.CheckoutActivityTest
Test: atest android.autofillservice.cts.AutofillValueTest

Change-Id: I48848dc1236161f481010dd78c3b9cbf5dd1faed
6 files changed