Add clearing of thread/fiber locals

Avoid memory leaks where the thread/fiber pool store's every local seen.

lib/graphiti/scope.rb

@@ -150,6 +150,11 @@ def future_with_fiber_locals(*args)
 
         result = yield(*args)
 
+        if execution_context_changed
+          thread_storage&.keys&.each { |key| Thread.current[key] = nil }
+          fiber_storage&.keys&.each { |key| Fiber[key] = nil }
+        end
+
         result
       end
     end