[Attributor] Use checkForAllUses instead of custom use tracking

AAMemoryBehaviorFloating used a custom use tracking mechanism even
though checkForAllUses exists and is already more powerful. Further,
AAMemoryBehaviorFloating uses AANoCapture to guarantee that there are no
aliases and following the uses is sufficient. This is an OK assumption
if checkForAllUses is used but custom tracking is easily out of sync
with AANoCapture and problems follow.