Stop the ridable horse's saddle from complaining that it can't switch parent to the ragdoll when the horse dies. It doesn't seem to need to switch, so I'm letting it be destroyed silently with an override - same as existing behaviour, but without the logging. Fixes "SwitchedParent Missed horse.corpse" server log spam.
Removed cases where I was doing specific mutable state checks in trigger InterestedInObject calls, not realising that InterestedInObject is also checked to see if we should allow a collider to detect that it LEFT a trigger. Fixes spawning a car on top of yourself and then noclipping out of it causing the game to consider you still in the triggers.
Fix BasePlayer movement references on the server in TriggerPlayerForce and TriggerMount. Moved BasePlayer vars that aren't used on the server at all into BasePlayer-Client, so this mistake is now prevented from being made again.