Make AccountNameEmailStore implement AddressDataManager::Observer

Make `AccountNameEmailStore` implement `AddressDataManager::Observer` to
ensure the `kAutofillNameAndEmailProfileNotSelectedCounter` pref is set
to an appropriate value when the `kAccuountNameEmail` profile gets
deleted.

Bug: 356845298
Change-Id: Ie96f0301daae9d7a28e350f952912d94bf6efb52
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6830065
Reviewed-by: Maksim Moskvitin <mmoskvitin@google.com>
Reviewed-by: Karol Sygiet <sygiet@google.com>
Commit-Queue: Paweł Stus <pawelstus@google.com>
Reviewed-by: Florian Leimgruber <fleimgruber@google.com>
Cr-Commit-Position: refs/heads/main@{#1500047}