Fix digital wellbeing banner position in portrait mode

The banner should be aligned to the start of the screen, not the center. This CL fixes DWB position for split tasks when device is unfolded.

Fix: 348200661
Bug: 345789862
Flag: EXEMPT bugfix
Test: Manual. Add a Digital Wellbeing (DWB) timer to 2 apps. Open these two apps in split mode. Unfold the device and go to Overview. The DWB banner should aligned correctly.
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:3d088e3899cfca516dfa8ae9699691ece2b914d9)
Merged-In: I0544b4a8eb85b00196373c8a4368e680abab222b
Change-Id: I0544b4a8eb85b00196373c8a4368e680abab222b