HackStudio: Add evaluate expression popup to debugger

This implements a dialog that can be used to evaluate a JS expression
in the HackStudio's Debugger context. It also implements simple
C++ Variable <-> JS Value conversion, allowing for JS expressions
to read/write variables in the debugger scope.

Currently, C++ structs are mapped to JS objects by way of a JS proxy,
however this leads to issues when printing, so this will be changed
in a later commit.

Userland/DevTools/HackStudio/Debugger/DebuggerGlobalJSObject.h

@@ -0,0 +1,34 @@
+/*
+ * Copyright (c) 2021, Hunter Salyer <thefalsehonesty@gmail.com>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/Weakable.h>
+#include <LibDebug/DebugInfo.h>
+#include <LibJS/Runtime/GlobalObject.h>
+
+namespace HackStudio {
+
+class DebuggerGlobalJSObject final
+    : public JS::GlobalObject
+    , public Weakable<DebuggerGlobalJSObject> {
+    JS_OBJECT(DebuggerGlobalJSObject, JS::GlobalObject);
+
+public:
+    DebuggerGlobalJSObject();
+
+    JS::Value get(const JS::PropertyName& name, JS::Value receiver, bool without_side_effects) const override;
+    bool put(const JS::PropertyName& name, JS::Value value, JS::Value receiver) override;
+
+private:
+    Optional<JS::Value> debugger_to_js(const Debug::DebugInfo::VariableInfo&) const;
+    Optional<u32> js_to_debugger(JS::Value value, const Debug::DebugInfo::VariableInfo&) const;
+
+private:
+    NonnullOwnPtrVector<Debug::DebugInfo::VariableInfo> m_variables;
+};
+
+}