rename numInstances to initialInstances in loadGltf methods.

when initialInstances > 0, don't wait for createInstance to be called to create corresponding GltfSceneAsset

thermion_dart/lib/src/filament/src/implementation/ffi_filament_app.dart

@@ -890,7 +890,7 @@ class FFIFilamentApp extends FilamentApp<Pointer> {
   ///
   Future<ThermionAsset> loadGltfFromBuffer(
       Uint8List data, Pointer animationManager,
-      {int numInstances = 1,
+      {int initialInstances = 1,
       bool keepData = false,
       int priority = 4,
       int layer = 0,
@@ -914,7 +914,7 @@ class FFIFilamentApp extends FilamentApp<Pointer> {
 
       var filamentAsset = await withPointerCallback<TFilamentAsset>((cb) =>
           GltfAssetLoader_loadRenderThread(engine, gltfAssetLoader,
-              data.address, data.length, numInstances, cb));
+              data.address, data.length, initialInstances, cb));
 
       if (filamentAsset == nullptr) {
         throw Exception("An error occurred loading the asset");

thermion_dart/lib/src/filament/src/interface/asset.dart

@@ -6,7 +6,6 @@ import 'package:thermion_dart/src/filament/src/interface/scene.dart';
 import 'package:thermion_dart/thermion_dart.dart';
 
 export 'geometry.dart';
-export 'gltf.dart';
 
 ///
 /// A high-level interface for a renderable object

thermion_dart/lib/src/filament/src/interface/filament_app.dart

@@ -291,11 +291,11 @@ abstract class FilamentApp<T> {
   Future setClearOptions(double r, double g, double b, double a,
       {int clearStencil = 0, bool discard = false, bool clear = true});
 
-  ///
+  /// See [FilamentViewerFFI.loadGltf] for details.
   ///
   ///
   Future<ThermionAsset> loadGltfFromBuffer(Uint8List data, T animationManager,
-      {int numInstances = 1,
+      {int initialInstances = 1,
       bool keepData = false,
       int priority = 4,
       int layer = 0,

thermion_dart/lib/src/filament/src/interface/gltf.dart

@@ -1,6 +0,0 @@
-class GLTF {
-  final String uri;
-  final int numInstances;
-
-  GLTF(this.uri, this.numInstances);
-}