Remove safe_filled_fields from BAM::OnDidFillOrPreviewForm

The only use case of `safe_filled_fields` in the BAM function is to pass
it to AutofillHandler so that it has access to the latest field values.

After having fixed crbug.com/40227496, there is no need anymore for
passing FormFieldData objects along with AutofillField objects just to
obtain the latest value, since AutofillField now contains this
information.

Bug: 40227071
Change-Id: I84fce531b0a89d5fce0caff1aaf6dcf1cc6ee2aa
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6734629
Commit-Queue: Jihad Hanna <jihadghanna@google.com>
Reviewed-by: Christoph Schwering <schwering@google.com>
Reviewed-by: Alex Rudenko <alexrudenko@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1487017}