HDR aware MSAA resolve

When supported and enabled, resolve MSAA using an HDR aware filter,
which improves anti-aliasing quality.

This is only supported with backends that support multi-sampled
framebuffer-fetch. Currently, only Metal on iOS and GLES.

Update remote ui.

libs/viewer/src/SimpleViewer.cpp

@@ -689,6 +689,9 @@ void SimpleViewer::updateUserInterface() {
         ImGui::Unindent();
 
         ImGui::Checkbox("MSAA 4x", &mSettings.view.msaa.enabled);
+        ImGui::Indent();
+            ImGui::Checkbox("Custom resolve", &mSettings.view.msaa.customResolve);
+        ImGui::Unindent();
 
         ImGui::Checkbox("SSAO", &mSettings.view.ssao.enabled);
         if (ImGui::CollapsingHeader("SSAO Options")) {