[iOS] AccountProfileMapper: Delete profile on managed identity removal

When a managed identity is removed from the device, the corresponding
profile should be deleted (since it would now be inaccessible).
This CL implements the logic to trigger deletions. However, since the
actual API to delete profiles from disk doesn't exist yet, for now it
only removes the profile's entry from ProfileAttributesStorage
(making the profile inaccessible, but leaving behind any data on disk).
There's a TODO to implement the actual deletion, once the API for that
exists.

Bug: 331783685
Change-Id: Ifd870fa34176c8bb3b70a63878988b16e09fd657
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6049424
Reviewed-by: Jérôme Lebel <jlebel@chromium.org>
Commit-Queue: Marc Treib <treib@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1388746}