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

----------

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

src/server/game/AI/SmartScripts/SmartScript.cpp

@@ -2380,7 +2380,7 @@ void SmartScript::ProcessAction(SmartScriptHolder& e, Unit* unit, uint32 var0, u
                 map = targets.front()->GetMap();
 
             if (map)
-                map->RemoveRespawnTime(SpawnObjectType(e.action.respawnData.spawnType), e.action.respawnData.spawnId, true);
+                map->Respawn(SpawnObjectType(e.action.respawnData.spawnType), e.action.respawnData.spawnId);
             else
                 TC_LOG_ERROR("sql.sql", "SmartScript::ProcessAction: Entry %d SourceType %u, Event %u - tries to respawn by spawnId but does not provide a map", e.entryOrGuid, e.GetScriptType(), e.event_id);
             break;