libtaskmanager: check if item before/after is a launcher before moving it
When separateLaunchers is disabled, also check if the item at before/after the new position is a launcher to avoid moving an actual window. BUG: 462508 FIXED-IN: 5.27
When separateLaunchers is disabled, also check if the item at before/after the new position is a launcher to avoid moving an actual window. BUG: 462508 FIXED-IN: 5.27