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>

Code/Tools/SceneAPI/SceneBuilder/Importers/AssImpMaterialImporter.cpp

@@ -6,6 +6,7 @@
  *
  */
 
+#include <API/EditorAssetSystemAPI.h>
 #include <SceneAPI/SceneBuilder/Importers/AssImpMaterialImporter.h>
 #include <AzCore/IO/FileIO.h>
 #include <AzCore/Serialization/SerializeContext.h>
@@ -196,11 +197,18 @@ namespace AZ
                     return texturePathRelativeToScene;
                 }
 
+                bool ok;
+                AZStd::string relativePath, rootPath;
+                AzToolsFramework::AssetSystemRequestBus::BroadcastResult(
+                    ok, &AzToolsFramework::AssetSystemRequestBus::Events::GenerateRelativeSourcePath,
+                    texturePathRelativeToScene.c_str(), relativePath, rootPath);
+
                 // The engine only supports relative paths to scan folders.
-                // Scene files may have paths to textures, relative to the scene file. Check for those, first.
-                if (AZ::IO::FileIOBase::GetInstance()->Exists(texturePathRelativeToScene.c_str()))
+                // Scene files may have paths to textures, relative to the scene file.
+                // Try to use a scanfolder relative path instead
+                if (ok)
                 {
-                    return texturePathRelativeToScene;
+                    return relativePath;
                 }