message: gltf_viewer: move "Animation" UI
  The Animation selector is now a top-level group (collapsed by default),
  previously it was in the Hierarchy group, which was non-intuitive.
  Also:
  Use indent() for consistency with other UI groups.
  Remove un-necessary usage of a lambda.
diff: @@ -445,23 +445,6 @@ void SimpleViewer::updateUserInterface() {
  }
  };
  - auto animationsTreeItem = [&]() {
  - size_t count = mAnimator->getAnimationCount();
  - int selectedAnimation = mCurrentAnimation;
  - ImGui::RadioButton("Disable", &selectedAnimation, 0);
  - for (size_t i = 0; i < count; ++i) {
  - std::string label = mAnimator->getAnimationName(i);
  - if (label.empty()) {
  - label = "Unnamed " + std::to_string(i);
  - }
  - ImGui::RadioButton(label.c_str(), &selectedAnimation, i + 1);
  - }
  - if (selectedAnimation != mCurrentAnimation) {
  - mCurrentAnimation = selectedAnimation;
  - mResetAnimation = true;
  - }
  - };
  -
  // Disable rounding and draw a fixed-height ImGui window that looks like a sidebar.
  ImGui::GetStyle().WindowRounding = 0;
  ImGui::SetNextWindowPos(ImVec2(0, 0));
  @@ -545,16 +528,28 @@ void SimpleViewer::updateUserInterface() {
  if (mAsset != nullptr) {
  if (ImGui::CollapsingHeader("Hierarchy")) {
  - if (mAnimator->getAnimationCount() > 0) {
  - intptr_t animationsNodeId = -1;
  - ImGuiTreeNodeFlags flags = ImGuiTreeNodeFlags_DefaultOpen;
  - if (ImGui::TreeNodeEx((const void*) animationsNodeId, flags, "Animations")) {
  - animationsTreeItem();
  - ImGui::TreePop();
  - }
  - }
  + ImGui::Indent();
  ImGui::Checkbox("Show bounds", &mEnableWireframe);
  treeNode(mAsset->getRoot());
  + ImGui::Unindent();
  + }
  +
  + if (mAnimator->getAnimationCount() > 0 && ImGui::CollapsingHeader("Animation")) {
  + ImGui::Indent();
  + int selectedAnimation = mCurrentAnimation;
  + ImGui::RadioButton("Disable", &selectedAnimation, 0);
  + for (size_t i = 0, count = mAnimator->getAnimationCount(); i < count; ++i) {
  + std::string label = mAnimator->getAnimationName(i);
  + if (label.empty()) {
  + label = "Unnamed " + std::to_string(i);
  + }
  + ImGui::RadioButton(label.c_str(), &selectedAnimation, i + 1);
  + }
  + if (selectedAnimation != mCurrentAnimation) {
  + mCurrentAnimation = selectedAnimation;
  + mResetAnimation = true;
  + }
  + ImGui::Unindent();
  }
  if (mEnableWireframe) {
  