Provide AutofillService to know how the dataset was shown to user

We introduce a filed for ui presentation in FillEventHistory.Event,
the type will be set for TYPE_DATASET_SHOWN and TYPE_DATASET_SELECTED.
The AutofillService can know which dataset is shown to user and which
type dataset user is clicked.

This change defines the definition and apply to TYPE_DATASET_SHOWN,
the TYPE_DATASET_SELECTED will be implemented on the follow up
change.

Bug: 223472350
Test: manual. build and boot pass. Test app and see dumpsys autofill
CTS-Coverage-Bug: 225310516

Change-Id: Ic221bd79e2ad512db5cd1ef8fd96c6bfae2ca616