Reintroduced spawning multiple instances of the same entity

The following was changed:
- The remapper in AZ::IdUtils now has an additional argument to tell it what to do when it encounters the same source entity id. The original behavior of ignoring the new entity id and returning the first occurrence is the default. The alternative behavior is to store the last known entity id and return that instead.
- Split the optional arguments for SpawnAllEntities and SpawnEntities.
- SpawnEntities now has an option to continue with the entity mapping from a previous spawn call or to start with a fresh mapping. The latter is the default as the former will come at a performance cost since the mapping table has to be reconstructed.
- Entities spawned using SpawnEntities and ReloadEntities now also get the correct entity mapping applied.
- Added several new unit tests to cover most of the new functionality.
- Fixed some places where the older API version was still called.

Code/Framework/AzFramework/AzFramework/Spawnable/SpawnableEntitiesManager.h

@@ -37,7 +37,7 @@ namespace AzFramework
         AZ_CLASS_ALLOCATOR(SpawnableEntitiesManager, AZ::SystemAllocator, 0);
 
         using EntityIdMap = AZStd::unordered_map<AZ::EntityId, AZ::EntityId>;
-
+        
         enum class CommandQueueStatus : bool
         {
             HasCommandsLeft,
@@ -57,7 +57,7 @@ namespace AzFramework
         // The following functions are thread safe
         //
 
-        void SpawnAllEntities(EntitySpawnTicket& ticket, SpawnEntitiesOptionalArgs optionalArgs = {}) override;
+        void SpawnAllEntities(EntitySpawnTicket& ticket, SpawnAllEntitiesOptionalArgs optionalArgs = {}) override;
         void SpawnEntities(
             EntitySpawnTicket& ticket, AZStd::vector<size_t> entityIndices, SpawnEntitiesOptionalArgs optionalArgs = {}) override;
         void DespawnAllEntities(EntitySpawnTicket& ticket, DespawnAllEntitiesOptionalArgs optionalArgs = {}) override;
@@ -114,6 +114,7 @@ namespace AzFramework
             Ticket* m_ticket;
             EntitySpawnTicket::Id m_ticketId;
             uint32_t m_requestId;
+            bool m_referencePreviouslySpawnedEntities;
         };
         struct DespawnAllEntitiesCommand
         {
@@ -183,12 +184,9 @@ namespace AzFramework
 
         CommandQueueStatus ProcessQueue(Queue& queue);
 
-        AZ::Entity* SpawnSingleEntity(const AZ::Entity& entityTemplate,
-            AZ::SerializeContext& serializeContext);
-
-        AZ::Entity* CloneSingleEntity(const AZ::Entity& entityTemplate,
-            EntityIdMap& templateToCloneEntityIdMap, AZ::SerializeContext& serializeContext);
-
+        AZ::Entity* CloneSingleEntity(
+            const AZ::Entity& entityTemplate, EntityIdMap& templateToCloneMap, AZ::SerializeContext& serializeContext);
+        
         bool ProcessRequest(SpawnAllEntitiesCommand& request);
         bool ProcessRequest(SpawnEntitiesCommand& request);
         bool ProcessRequest(DespawnAllEntitiesCommand& request);