Splits OnObtainGhostCloth, OnObtainGhostVespa

[AlexKnauth]

Part of #57, but not the whole.

Testing:

• [x] Doesn't split OnObtainGhostVespa on getting Blessence from Hive Knight
• [x] Splits OnObtainGhostVespa on getting Vespa after Hive Knight has been dead, even without Hiveblood
• [x] Splits OnObtainGhostVespa on getting Vespa on 1221 where Hive Knight doesn't exist, even without Hiveblood
• [x] Doesn't split OnObtainGhostCloth on getting Blessence from the Mantis Traitors opening for Traitor Lord
• [x] Doesn't split OnObtainGhostCloth on getting Blessence from Traitor Lord
  • Complication: When Cloth and I killed Traitor Lord, I didn't notice any essence, despite the EssenceAlways mod being on?
  • Just test it on killing Traitor Lord without Cloth there
• [x] Splits OnObtainGhostCloth on getting Cloth after Traitor Lord has been dead