Include source activity in trampoline bounds inheritance

Currently trampoline task bounds are inherited by detecting the visible
tasks of a trampoline and ensuring the bounds are propagated from one to
the other. Some trampoline tasks launch too quickly to become visible
and are thus not detected in this trampoline bounds inheritance. However
the source of the current launch corresponds to the previous launch in
the trampoline sequence. So instead, we should also check the source
activity if available and then any visible tasks for trampoline bounds
inheritance.

Flag: EXEMPT bug fix
Test: atest WmTests:DesktopModeLaunchParamsModifierTests
Bug: 417599443
Change-Id: I73da647a65d2b35f63b26201ab945cc15216e563