LibGUI: Take ProcessManager's process view and turn it into GTableView.

Make it sufficiently generic that it can be reused for any table data. :^)

Applications/ProcessManager/ProcessTableView.h

@@ -0,0 +1,24 @@
+#pragma once
+
+#include <LibGUI/GTableView.h>
+#include <AK/Function.h>
+#include <unistd.h>
+
+class ProcessTableModel;
+
+class ProcessTableView final : public GTableView {
+public:
+    explicit ProcessTableView(GWidget* parent);
+    virtual ~ProcessTableView() override;
+
+    pid_t selected_pid() const;
+
+    Function<void(String)> on_status_message;
+
+private:
+    virtual void timer_event(GTimerEvent&) override;
+
+    ProcessTableModel& model();
+    const ProcessTableModel& model() const;
+};
+