[Fill Dialog Improvements] Implement Fill Dialog improvements

Implement Fill Dialog improvements.
This change achieves a multitude of changes.
1. Disable pre-trigger flow
2. Show fill dialog if applicable
3. Reset fill dialog state so that fill dialog can be retriggered
   on another fill request in the same session. This part isn't
   tested yet, and would be done later.

Bug: 377868687
Flag: android.service.autofill.improve_fill_dialog_aconfig
Test: atest CtsAutoFillServiceTestCases
      atest android.autofillservice.cts.dialog.LoginActivityTest

Change-Id: I959ecc4e98d26f059a6a354f6c83d653555e89c3