Inject session id on all AutofillIds kept in the service.

Android Q introduce the FLAG_DELAY_SAVE, which allows the autofill service to delay the SAVE UI by
keeping the session open. But this approach introduces a new problem, as fields from different
activities could have the same AutofillId.

Test: atest MultiScreenLoginTest#testSaveBothFieldsCustomDescription_sameIds
Test: atest AutofillIdTest
Test: atest CtsAutoFillServiceTestCases # sanity check

Fixes: 113593220

Change-Id: Ibd187f5c58c150f820972fcab6d88217294ffe2d