Add natives to properly use TFCond_TmpDamageBonus

Relevant changes to TF2_AddCondition included:
"Inflictor" changed to "Provider".
Provider is now allowed to be any entity (for instance, dispensers).
Moved actual call to TF2_AddCond to its own function, called by
TF2_AddCondition native (as well as by the TmpDamageBonus natives).
For the few of these that are split out, it would probably be wise now to name the function not able to be located, especially since it may be non-obvious when getting it for addcond when not calling it directly.