perf(thread saftey): All Engines are now thread safe

Previously engines were not thread safe, a seperate engine would be
needed for every thread. This is no longer the case. This allows for
much more efficient parallel execution

src/include/gridfire/exceptions/error_scratchpad.h

@@ -0,0 +1,14 @@
+#pragma once
+
+#include <string>
+#include <stdexcept>
+
+#include "gridfire/exceptions/error_gridfire.h"
+
+namespace gridfire::exceptions {
+    class ScratchPadError : public GridFireError {
+    public:
+        explicit ScratchPadError(const std::string& msg)
+            : GridFireError("ScratchPadError: " + msg) {}
+    };
+}