Find activity in task with same user

FLAG_ACTIVITY_REORDER_TO_FRONT will cause the launched activity to be
brought to the front of its task's history if it is already running.
Without considering the userId information might bring the different
user’s activity to front. Same reason as clear-top operation.

This CL considers the userId to find the existing activity with the
same user.

Bug: 243459513
Bug: 237742126
Test: atest ActivityStarterTests
Change-Id: I21e8fa1d65b2b456016210a3534c493a9607b4ba