ProcessManager: Rename it to SystemMonitor

This is a more appropriate name now that it does a lot
more than just manage processes ^)

Applications/SystemMonitor/ProcessStacksWidget.h

@@ -0,0 +1,21 @@
+#pragma once
+
+#include <LibGUI/GTextEditor.h>
+#include <LibGUI/GWidget.h>
+
+class CTimer;
+
+class ProcessStacksWidget final : public GWidget {
+    C_OBJECT(ProcessStacksWidget)
+public:
+    explicit ProcessStacksWidget(GWidget* parent);
+    virtual ~ProcessStacksWidget() override;
+
+    void set_pid(pid_t);
+    void refresh();
+
+private:
+    pid_t m_pid { -1 };
+    GTextEditor* m_stacks_editor { nullptr };
+    CTimer* m_timer { nullptr };
+};