Send flag to disable gestures when split layout is animating

* Previously we were only sending the signal when starting/opening
split apps.
* Now sending it also for divider swap and switching between apps
in flex split and general divider flings

Test: Manual
Bug: 391894192
Flag: EXEMPT bugfix
Change-Id: Icb41f68e06b6c3ff4a5ff96047f4fa44ed8ff8c2