Fix Entity id consistency issue & refactor prefab workflows/tests (#4373)

* Fix Entity id consistency issue & refactor prefab workflows/test framework

Signed-off-by: chiyteng <chiyteng@amazon.com>

* Update comments

Signed-off-by: chiyteng <chiyteng@amazon.com>

* Modify CreatePrefab and remove extra spaces

Signed-off-by: chiyteng <chiyteng@amazon.com>

* Address comments

Signed-off-by: chiyteng <chiyteng@amazon.com>

* Refactor prefab instance constructors

Signed-off-by: chiyteng <chiyteng@amazon.com>

* Remove commented out code

Signed-off-by: chiyteng <chiyteng@amazon.com>

Code/Framework/AzToolsFramework/Tests/Prefab/PrefabTestDomUtils.cpp

@@ -56,7 +56,7 @@ namespace UnitTest
         }
 
         void ValidateInstances(
-            const TemplateId& templateId,
+            TemplateId templateId,
             const PrefabDomValue& expectedContent,
             const PrefabDomPath& contentPath,
             bool isContentAnInstance,
@@ -204,7 +204,7 @@ namespace UnitTest
         }
 
         void ValidateEntitiesOfInstances(
-            const AzToolsFramework::Prefab::TemplateId& templateId,
+            AzToolsFramework::Prefab::TemplateId templateId,
             const AzToolsFramework::Prefab::PrefabDom& expectedPrefabDom,
             const AZStd::vector<EntityAlias>& entityAliases)
         {
@@ -219,7 +219,7 @@ namespace UnitTest
         }
 
         void ValidateNestedInstancesOfInstances(
-            const AzToolsFramework::Prefab::TemplateId& templateId,
+            AzToolsFramework::Prefab::TemplateId templateId,
             const AzToolsFramework::Prefab::PrefabDom& expectedPrefabDom,
             const AZStd::vector<InstanceAlias>& nestedInstanceAliases)
         {