Replace [GREYConfiguration sharedInstance] with ScopedSynchronizationDisabler.

This is part of EG1 to EG2 migration, which involves moving
EarlGrey code from app-side helpers into test code.
EarlGrey2 has multiprocess architecture,
where Chrome Test and Chrome App are separate processes.

Updated signin_interaction_controller_egtest and its helpers.

Change-Id: I46fefaaf0a6698e8847c19f269332cd30683dc1b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1738426
Commit-Queue: Maksym Onufriienko <monufriienko@chromium.org>
Reviewed-by: Eugene But <eugenebut@chromium.org>
Cr-Commit-Position: refs/heads/master@{#684544}
4 files changed