[iOS] Replace Cancel button with back button in Autofill Profile Edit Settings

A cycle of pressing "Edit" and "Cancel" causes unwanted behaviour in the
settings view, probably causing data corruption and crashes, therefore,
the cancel button in the edit view is replaced with the back button.

This is a reland of http://crrev.com/c/6372622 after fixing the tests.

Bug: 397234755
Change-Id: I3b293125ca56cd77a218b4a1a663eabefb7ca10d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6381852
Reviewed-by: Gauthier Ambard <gambard@chromium.org>
Commit-Queue: Gauthier Ambard <gambard@chromium.org>
Auto-Submit: Vidhan Jain <vidhanj@google.com>
Cr-Commit-Position: refs/heads/main@{#1435993}