Core/Game: Rewrote the ScriptMgr to support script reloading.

* Finally this commit enables dynamic script hotswapping
  and finished the PR #15671.
* Split the storage layout to use optimized storages
  for database bound and unbound scripts.
* Add several unload workers to reload scripts correctly
  -> Requires further investigation.
* Fixes memory leaks in ScriptMgr when dropping invalid scripts.
* Fixes VehicleScripts
* Makes OutdoorPvP scripts reloadable
* Makes InstanceMapScripts reloadable
* Makes CommandScripts reloadable

(cherry picked from commit 9cc97f226d)

src/server/game/Instances/InstanceScript.cpp

@@ -29,6 +29,8 @@
 #include "Pet.h"
 #include "WorldSession.h"
 #include "Opcodes.h"
+#include "ScriptReloadMgr.h"
+#include "ScriptMgr.h"
 
 BossBoundaryData::~BossBoundaryData()
 {
@@ -36,6 +38,18 @@ BossBoundaryData::~BossBoundaryData()
         delete it->Boundary;
 }
 
+InstanceScript::InstanceScript(Map* map) : instance(map), completedEncounters(0)
+{
+#ifdef TRINITY_API_USE_DYNAMIC_LINKING
+    uint32 scriptId = sObjectMgr->GetInstanceTemplate(map->GetId())->ScriptId;
+    auto const scriptname = sObjectMgr->GetScriptName(scriptId);
+    ASSERT(!scriptname.empty());
+   // Acquire a strong reference from the script module
+   // to keep it loaded until this object is destroyed.
+    module_reference = sScriptMgr->AcquireModuleReferenceOfScriptName(scriptname);
+#endif // #ifndef TRINITY_API_USE_DYNAMIC_LINKING
+}
+
 void InstanceScript::SaveToDB()
 {
     std::string data = GetSaveData();