Tied up a few loose ends to support deeply nested property groups.

Simplified the call back for MaterialTypeSourceData::EnumeratePropertyGroups while also providing more data.
Made the Material Inspector join nested property group display names to be like "Layer 1 | Base Color", since the leaf property groups are shown as a flat list in the inspector.
Fixed CreateMaterialAssetFromSourceData to include the imported json files in the list of sourceDependencies. This triggers the Material Editor to hot-reload when one of these json files changes.
Updated a few places that were still assuming only one level of property group.
Updated EditorMaterialComponentInspector to apply the per-property-group material functors, before it was still only applying the top-level onces.
Moved some accessor function implementations to the cpp files, per feedback on another already-merged PR.

Testing:
Made changes to MinimalMultilayerPbr (in AtomSampleViewer) to use nested property groups, and saw the correct behavior in the Material Editor's property inspector.
Used MaterialComponent's property inspector to edit a StandardPbr material instance. Confrimed that functors were correctly controlling property visibility by enabling and disabling things like emissive and clear coat.
Used MaterialComponent's property inspector to edit a MinimalMultilayerPbr material instance. Saw all the expected groups and properties show up. Confirmed that per-group functors were correctly controlling property visibility.
Used MaterialComponent's property inspector to export a material instance and confirmed the .material file included the expected properties.

Signed-off-by: santorac <55155825+santorac@users.noreply.github.com>

Gems/Atom/RPI/Code/Source/RPI.Reflect/Material/MaterialNameContext.cpp

@@ -117,6 +117,20 @@ namespace AZ
             shaderOptionName = m_shaderOptionNameContext + shaderOptionName;
             return true;
         }
+        
+        bool MaterialNameContext::HasContextForProperties() const
+        {
+            return !m_propertyIdContext.empty();
+        }
 
+        bool MaterialNameContext::HasContextForSrgInputs() const
+        {
+            return !m_srgInputNameContext.empty();
+        }
+
+        bool MaterialNameContext::HasContextForShaderOptions() const
+        {
+            return !m_shaderOptionNameContext.empty();
+        }
     } // namespace RPI
 } // namespace AZ