Put starting surface in task for embedded activity

So the layer and position won't be disturbed by the parent activity.
It also isolates the container effect such as the window won't be
affected if the task fragment has crop.

Bug: 201261613
Bug: 189385912
Test: atest ActivityRecordTests#testStartingWindowInTaskFragment
Change-Id: Ifa866d26d31c655662f13aa5978078aa511ad116