Avoid extra relaunch when rotating side-by-side apps

Update configuration with WM first and check if the stacks need to be
resized due to the update. If so, let activity manager resize the stacks
inline, instead of letting WM schedule another pass of resizeStack. This
way the configuration will be updated to the latest before ensureActivity-
ConfigurationLocked, and we don't need another relaunch there.

bug: 27834014

Change-Id: Ib761a96cada0c3247b0480f18370670c593159da