[desktop] Add basic Frametime/FPS overlay (#3537)

Just displays min, max, avg frametime/fps, alongside a chart of FPS in
the last 30 seconds.

Notes:
- Qt Charts is now required
- FPS/frametime collector now runs 2x as often. TODO: keep status bar at
  500ms, but put perf overlay at 250ms

Signed-off-by: crueter <crueter@eden-emu.dev>

Reviewed-on: https://git.eden-emu.dev/eden-emu/eden/pulls/3537
Reviewed-by: Lizzie <lizzie@eden-emu.dev>
Reviewed-by: MaranBr <maranbr@eden-emu.dev>

src/yuzu/render/performance_overlay.h

@@ -0,0 +1,73 @@
+// SPDX-FileCopyrightText: Copyright 2026 Eden Emulator Project
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#pragma once
+
+#include <deque>
+#include <QWidget>
+
+namespace VideoCore {
+class ShaderNotify;
+}
+namespace Core {
+struct PerfStatsResults;
+}
+namespace Ui {
+class PerformanceOverlay;
+}
+
+class QLineSeries;
+class QChart;
+class QChartView;
+class QValueAxis;
+class MainWindow;
+
+class PerformanceOverlay : public QWidget {
+    Q_OBJECT
+
+public:
+    explicit PerformanceOverlay(MainWindow* parent = nullptr);
+    ~PerformanceOverlay();
+
+protected:
+    void paintEvent(QPaintEvent* event) override;
+
+    void mousePressEvent(QMouseEvent* event) override;
+    void mouseMoveEvent(QMouseEvent* event) override;
+    void closeEvent(QCloseEvent *event) override;
+
+private:
+    void resetPosition(const QPoint& pos);
+    void updateStats(const Core::PerfStatsResults &results, const VideoCore::ShaderNotify &shaders);
+
+    MainWindow *m_mainWindow = nullptr;
+    Ui::PerformanceOverlay* ui;
+
+    // colors
+    QColor m_background{127, 127, 127, 190};
+
+    QPoint m_offset{25, 75};
+
+    // frametime
+    const size_t NUM_FRAMETIME_SAMPLES = 300;
+    std::deque<double> m_frametimeSamples;
+
+    // fps
+    const size_t NUM_FPS_SAMPLES = 120;
+    qreal m_xPos = 0;
+    std::deque<double> m_fpsSamples;
+    std::deque<QPointF> m_fpsPoints;
+
+    // drag
+    QPoint m_drag_start_pos;
+
+    // fps chart
+    QLineSeries *m_fpsSeries = nullptr;
+    QChart *m_fpsChart = nullptr;
+    QChartView *m_fpsChartView = nullptr;
+    QValueAxis *m_fpsX = nullptr;
+    QValueAxis *m_fpsY = nullptr;
+
+signals:
+    void closed();
+};