Move stroke commit request assembly behind service helper

src/legacy_canvas_stroke_commit_services.h

@@ -165,6 +165,19 @@ inline void bind_legacy_canvas_stroke_commit_face_inputs(
         std::forward<BindFaceSamplerRole>(bind_face_sampler_role));
 }
 
+[[nodiscard]] inline LegacyCanvasStrokeCommitRequest make_legacy_canvas_stroke_commit_request(
+    const std::array<LegacyCanvasStrokeCommitFace, 6>& faces,
+    const pp::paint_renderer::CanvasStrokeCommitSequencePlan& sequence,
+    const LegacyCanvasStrokeCommitCallbacks& callbacks)
+{
+    return LegacyCanvasStrokeCommitRequest {
+        .context = "Canvas::stroke_commit",
+        .faces = faces,
+        .sequence = sequence,
+        .callbacks = callbacks,
+    };
+}
+
 template <typename SetupShader, typename DrawPlane>
 inline void execute_legacy_canvas_stroke_commit_erase(
     SetupShader&& setup_shader,