** Issue:
When UNOp2 is enabled, TwoScreensSigninCoordinator in charge to show
the UpgradePromo, using SigninScreenCoordinator and
HistorySyncCoordinator.
SigninScreenMediator uses UserSigninLogger for the upgrade promo
instead of UpgradeSigninLogger.
Also when the user is signed in, HistorySyncCoordinator doesn't use
records any metrics/prefs related to the UpgradePromo.

** Fix:
This patch updates TwoScreensSigninCoordinator to call:
  on start:
+[UserSigninLogger logSigninStartedWithAccessPoint:
                             accountManagerService:]
  on finish:
+[UserSigninLogger logSigninCompletedWithResult:
                                   addedAccount:]
Those 2 methods are only called when the access point is
ACCESS_POINT_SIGNIN_PROMO.

EGTests are done in crrev.com/c/4931414.

(cherry picked from commit 267cc25fc32085c6a92dbc99b2b8f5147f179772)

Fixed: 1491096
Change-Id: Iad60371ab7c4e25d933da8b25de47912b63c7010
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4925234
Auto-Submit: Jérôme Lebel <jlebel@chromium.org>
Commit-Queue: Mikel Astiz <mastiz@chromium.org>
Reviewed-by: Victor Vianna <victorvianna@google.com>
Reviewed-by: Mikel Astiz <mastiz@chromium.org>
Cr-Original-Commit-Position: refs/heads/main@{#1208374}
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4931878
Reviewed-by: Krishna Govind <govind@chromium.org>
Owners-Override: Krishna Govind <govind@chromium.org>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Cr-Commit-Position: refs/branch-heads/6061@{#4}
Cr-Branched-From: ce242f54d0a5a1fb245c005162dc57361689e904-refs/heads/main@{#1208194}