Make rendering stats thread safe [Core feature] (#4059)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Adrian Cojocaru <adrian.cojocaru92@yahoo.com>
Co-authored-by: Bart Louwers <bart.louwers@gmail.com>

include/mbgl/gfx/context.hpp

@@ -13,6 +13,8 @@
 
 #include <memory>
 #include <string>
+#include <mutex>
+#include <shared_mutex>
 
 namespace mbgl {
 
@@ -93,6 +95,16 @@ public:
     gfx::RenderingStats& renderingStats() { return stats; }
     const gfx::RenderingStats& renderingStats() const { return stats; }
 
+    void threadSafeAccessRenderingStats(const std::function<void(RenderingStats&)>& function) {
+        std::scoped_lock lock(renderingStatsMutex);
+        function(stats);
+    }
+
+    RenderingStats threadSafeCopyRenderingStats() {
+        std::shared_lock lock(renderingStatsMutex);
+        return stats;
+    }
+
 #ifndef NDEBUG
     virtual void visualizeStencilBuffer() = 0;
     virtual void visualizeDepthBuffer(float depthRangeSize) = 0;
@@ -174,6 +186,7 @@ protected:
     virtual std::unique_ptr<RenderbufferResource> createRenderbufferResource(RenderbufferPixelType, Size) = 0;
     virtual std::unique_ptr<DrawScopeResource> createDrawScopeResource() = 0;
 
+    std::shared_mutex renderingStatsMutex;
     gfx::RenderingStats stats;
     ContextObserver* observer;
 };