Add z-order regions for task child layers

There are multiple components in both WM core and WM shell that add
child layers to task layers. Most of them used to use the max and min
value of integers to put themselves in front of and behind activities,
and occasionally there were inadvertent occlusions among them. This CL
adds a few regions to known components who don't need to interleave
themselves with activities and/or task fragments. Since we own all these
components we can trust all components use the defined value so
enforcement isn't necessary.

Bug: 244455401
Test: Build.
Change-Id: Iaa267b2ba53053bf25f3c6d590f50ceafafbf0a3