Fix DWB placement in grouped task view

In grouped task view, DWB banners will now rotate properly when phone is
in landscape or seascape orientation. Also fixes a couple of minor
existing issues with the bottom task not displaying correctly in the
first place.

Fixes: 208357326
Fixes: 216218406

Test: Tested locally on Pixel 6, using landscape, seascape, and
portrait. Double-checked with task proportions changed, RtL/LtR, and
split top/split left/split right initialization.

Change-Id: I945f9937d2d4d784c0c74a006c7d0680daf628c2