ATOM-15549 [RHI][Vulkan][Android] Add sponza from AtomContent to replace as model for samples using bistro

JIRA: https://jira.agscollab.com/browse/ATOM-15549

Registry/assets_scan_folders.setreg

@@ -7,7 +7,8 @@
             {
                 "SourcePaths":
                 [
-                    "Gems/Atom/Tools/MaterialEditor"
+                    "Gems/Atom/Tools/MaterialEditor",
+                    "Gems/AtomContent/Sponza"
                 ]
             },
             "UiBasics":