Add a new Autofill FillEvent - for when the user taps a field.

Test: atest
android.autofillservice.cts.inline.InlineFillEventHistoryTest

atest android.autofillservice.cts.dropdown.FillEventHistoryTest

Bug: 266231634

Change-Id: I96d5aea6a0e8d834ffda5eb593f9969a7b1826e8
Merged-In: I96d5aea6a0e8d834ffda5eb593f9969a7b1826e8