Fix the broken tests when AppStorage is enabled(Part III).

When the kAppServiceStorage flag is enabled, AppService blocks the
app publishers creating until it's ready, after reading from the
AppStorage file. This affects some tests, e.g.
QuickAnswersStateAshTest.*. Those tests crash because no data path
for the profile:
Received signal 11 SEGV_MAPERR 000000000017
...
#9 0x7f445a1f27b7 base::FilePath::Append()
#10 0x7f44710376e4 ash::BrowserContextHelper::GetBrowserContextPathByUserIdHash()
#11 0x55e7a2294d85 ash::ProfileHelperImpl::GetUserByProfile()
#12 0x55e7a22944d7 ash::ProfileHelper::IsPrimaryProfile()
#13 0x55e7b07a2a23 NearbySharingServiceFactory::IsNearbyShareSupportedForBrowserContext()
...

Modify the test setup process to create the user manager first, then
create the profile to align with the production code.

Remove `scoped_user_manager_` in TestExtensionSystem, as that has been moved to TestProfile.

BUG=1385932, b:307623506

Change-Id: Ib07f4a5a347893b7eab8d3bb8cd870c6831898c2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5076443
Reviewed-by: Reilly Grant <reillyg@chromium.org>
Commit-Queue: Nancy Wang <nancylingwang@chromium.org>
Reviewed-by: Xiaohui Chen <xiaohuic@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1235337}