Fix issue with split screen launch bounds

- In O, the fullscreen stack was resized once we enter splitscreen (and
  is updated with the tempOtherTaskBounds as we resize for minimized
  state). However, in P, since we are creating a new stack for each task,
  the launch of a task while in splitscreen now falls into
  TaskStack.updateBoundsForWindowModeChange() which incorrectly calculates
  the bounds of the secondary stack using the minimized bounds of the
  primary stack. Subsequent launches are fine because the stack already
  exists and is just being brought forward.

Bug: 73745166
Test: atest CtsActivityManagerDeviceTestCases:ActivityManagerSplitScreenTests
Test: Enter split screen, launch an app from scratch and ensure it
      animates to the right place

Change-Id: I7da856b9bb88db0db9616d56bb9fefdce918d7c3