New Autofill API: CustomDescription.batchUpdates()

This API allows the service to apply updates in the save UI remote view, when
a given condition applies.

Test: cts-tradefed run commandAndExit cts-dev -m CtsAutoFillServiceTestCases
Test: cts-tradefed run commandAndExit cts-dev -m CtsAutoFillServiceTestCases -t android.autofillservice.cts.CustomDescriptionTest
Test: cts-tradefed run commandAndExit cts-dev -m CtsAutoFillServiceTestCases -t android.autofillservice.cts.CustomDescriptionUnitTest
Test: cts-tradefed run commandAndExit cts-dev -m CtsAutoFillServiceTestCases -t android.autofillservice.cts.BatchUpdatesTest

Fixes: 63933969

Change-Id: I5002f231cd2029463b81a68fb3acd9bf1ae5964a