Align locale with activity that start the task

System apps(Settings) are able to embed activities that don't belong
to them, which may cause users to set different languages in embedded
apps and display two different languages in one app.

- Align locale with the activity that start the task activity in
  activity embedding feature.

- Since phone doesn't include the activity embedding feature, adding
  a hidden API for system app to align the locale.

Bug: 199277729
Test: Verified on Cuttlefish
Change-Id: Ic23a93a492b6d0fecb5a9519396701273b751d39