Fix python fbx tests (#2171)

* Update fbx test dbgsg files

Remove rc products from fbx test expected output
Update warning counts for 2 of the tests - these are due to missing material properties
Add SkipAtomOutput setting to disable atom material and mesh processing in scene as these pull in a lot of external dependencies to Process
Removed BlendShapeData and MeshData debug output of positions/normals/faces
Updated ManifestImportRequestHandler to remove warning about Joining 2 absolute paths
Updated AssImpMaterialImporter to use new GenerateRelativeSourcePath API to fix issue where relative path generation failed with tmp project directories

Signed-off-by: amzn-mike <80125227+amzn-mike@users.noreply.github.com>

* Add comment for setting

Signed-off-by: amzn-mike <80125227+amzn-mike@users.noreply.github.com>

* Add override dbgsg file to python test

The mesh optimizer specifically avoids creating optimized nodes for nodes that are not selected, resulting in a different scene graph that requires a different dbgsg file to compare with

Signed-off-by: amzn-mike <80125227+amzn-mike@users.noreply.github.com>

* Replace hardcoded passing of specific registry setting to instead pass all registry settings to AssetBuilder

Signed-off-by: amzn-mike <80125227+amzn-mike@users.noreply.github.com>

Gems/Atom/RPI/Code/Source/RPI.Builders/Model/ModelExporterComponent.cpp

@@ -31,6 +31,7 @@
 #include <cinttypes>
 
 #include <Atom/RPI.Reflect/Material/MaterialAsset.h>
+#include <AzCore/Settings/SettingsRegistry.h>
 
 namespace AZ
 {
@@ -40,6 +41,15 @@ namespace AZ
 
         ModelExporterComponent::ModelExporterComponent()
         {
+            // This setting disables model output (for automated testing purposes) to allow an FBX file to be processed without including
+            // all the dependencies required to process a model.  
+            auto settingsRegistry = AZ::SettingsRegistry::Get();
+            bool skipAtomOutput = false;
+            if (settingsRegistry && settingsRegistry->Get(skipAtomOutput, "/O3DE/SceneAPI/AssetImporter/SkipAtomOutput") && skipAtomOutput)
+            {
+                return;
+            }
+
             BindToCall(&ModelExporterComponent::ExportModel);
         }