Ensure the activity type is set to the activity

This CL reverts the changes in commit f9203082. The activity type
was an attribute in ActivityRecord, but added as part of window
configuration after unify. To keep the same behavior as it used to
be, this CL makes sure the activity type is set to the activity's
requested override configuration.

In general, the activity type is not necessary to be set while
creating a Task. The activity type of a Task is determined while
the first activity added into the task.

Also throw exceptions on debuggable builds if activity type is
changed once set.

Bug: 274751858
Test: wm presubmit
Test: drag contacts to split-screen
Change-Id: Ibf18bd6ec932ffef21bf556beea9004c25473203