ATOM-14065 fix problems with material editor details group property descriptions

Moved the code that automatically appended a script variable name to a property description out of the dynamic property class and into the material property conversion utility functions.

Added proper descriptions for the material type and parent material placeholder properties

https://jira.agscollab.com/browse/ATOM-14065

Gems/Atom/Tools/AtomToolsFramework/Code/Source/DynamicProperty/DynamicProperty.cpp

@@ -211,10 +211,7 @@ namespace AtomToolsFramework
 
     AZStd::string DynamicProperty::GetDescription() const
     {
-        return AZStd::string::format("%s%s(Script Name = '%s')",
-            m_config.m_description.c_str(),
-            m_config.m_description.empty() ? "" : "\n",
-            m_config.m_id.GetCStr());
+        return m_config.m_description;
     }
 
     AZ::Crc32 DynamicProperty::GetVisibility() const