Consistently use index instead of virtual id in AutofillProvider.

AutofillProvider.isDatalistField expects the (0-based) index of a
form field in its form. However, it is currently called with
the child's virtual id inside notifyVirtualViewEntered and
notifyVirtualViewExited.

This is a bug that would result in an out of bounds exception
if it were not for the fact the the lower 16 bit of the virtual
id correspond to the field index and isDatalistField casts
its int argument to a 16-bit short.

This CL moves all notifyVirtualView* methods of AutofillProvider
to take field indices instead of field virtual ids.

Bug: 1482048
Change-Id: I575e1ab1455f181e9d41113694bbb8df72f85642
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4866321
Commit-Queue: Jan Keitel <jkeitel@google.com>
Code-Coverage: findit-for-me@appspot.gserviceaccount.com <findit-for-me@appspot.gserviceaccount.com>
Reviewed-by: Dominic Battre <battre@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1196544}