Move FakePlusAddressService to a central location.

There are currently 4 places that all use some variation of a
FakePlusAddressService. This CL consolidates them into a single class.

Bug: 322279583
Change-Id: I7b0d37f940ad270c29310787b44e49cfabfa43f6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5366040


Commit-Queue: Jan Keitel <jkeitel@google.com>
Reviewed-by: Florian Leimgruber <fleimgruber@google.com>
Cr-Commit-Position: refs/heads/main@{#1271549}