Core/Misc: Various dynspawn cleanup and refactors split off from pooling rewrite:

- Map::RemoveRespawnTime(SpawnObjectType, LowType, doRespawn) split into Map::Respawn and Map::RemoveRespawnTime, without the extra boolean
- Map::RemoveRespawnTime(RespawnInfo*) merged into Map::DeleteRespawnInfo(RespawnInfo*) and is now private
- Map::DeleteRespawnInfo(void) renamed to Map::UnloadAllRespawnInfos to properly describe what it does
- Map::ProcessRespawns now actually saves the delayed respawn time to DB if the respawn was delayed
- Map::AddRespawnInfo now takes const reference, and returns success as a boolean
- Map::AddRespawnInfo no longer offers an unused "replace" parameter
- Map::DeleteRespawnInfo no longer offers a variety of unused private overloads
- Map::SaveRespawnTime no longer offers a tantalizing writeDB parameter. Parameter is now called "startup" to properly describe what it does.
- Map::SaveRespawnInfoDB now takes RespawnInfo reference instead of all the various fields. Still public because compatibility mode. QQ.
- Map::GetWorldObjectBySpawnId sanitized
- Map::GetXRespawnTime methods sanitized to all go through Map::GetRespawnTime

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Core/DB: Unify `creature_respawn` and `gameobject_respawn` into a single `respawn` table

src/server/scripts/Commands/cs_gobject.cpp

@@ -27,6 +27,7 @@ EndScriptData */
 #include "DatabaseEnv.h"
 #include "DBCStores.h"
 #include "GameEventMgr.h"
+#include "GameObject.h"
 #include "Language.h"
 #include "Log.h"
 #include "MapManager.h"