Add BarModelEditor and improve layouts

Add the new class `BarModelEditor` which is intended to become a new way
to adjust values of float models.

Simplify the layout in `LadspaMatrixControlDialog` by removing some
nested layouts. Remove the "Parameters" column.

Adjust `LadspaMatrixControlView` to implement the following changes:
* Show the name of the control next to toggle buttons (`LedCheckBox`).
* Use the new `BarModelEditor` for integer and float types.
* SHow the name of the control next to time based parameters that use
`TempoSyncKnob`.

The names are shown so that the "Parameters" column can be removed.

Technical details
------------------
The class `LadspaMatrixControlDialog` now creates a widget that contains
the matrix layout with the controls. This widget is then added to a
scroll area. The layout is populated in the new method
`arrangeControls`.

Add some helper methods to `LadspaMatrixControlDialog` which retrieve
the `LadspaControls` instance and the number of channels.

Add the implementation of `BarModelEditor` to `src/gui/CMakeLists.txt`.

TODOs
------
Extract common code out of the `Knob` class so that it can be reused by
`BarModelEditor`.

include/BarModelEditor.h

@@ -0,0 +1,57 @@
+/*
+ * BarModelEditor.h - edit model values using a bar display
+ *
+ * Copyright (c) 2023-now Michael Gregorius
+ *
+ * This file is part of LMMS - https://lmms.io
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public
+ * License along with this program (see COPYING); if not, write to the
+ * Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+ * Boston, MA 02110-1301 USA.
+ *
+ */
+
+#include "AutomatableModelView.h"
+
+#include <QWidget>
+
+namespace lmms::gui
+{
+
+class BarModelEditor : public QWidget, public FloatModelView
+{
+public:
+	BarModelEditor(QString text, FloatModel * floatModel, QWidget * parent = nullptr);
+
+	// Define how the widget will behave in a layout
+	QSizePolicy sizePolicy() const;
+
+	virtual QSize minimumSizeHint() const override;
+
+	virtual QSize sizeHint() const override;
+
+protected:
+	virtual void paintEvent(QPaintEvent *event) override;
+
+	virtual void contextMenuEvent(QContextMenuEvent * me) override;
+	virtual void mouseDoubleClickEvent(QMouseEvent * me) override;
+
+private:
+	void connectToModelSignals();
+
+private:
+	QString const m_text;
+};
+
+}