Fix EffectRackView appearance (GUI). (#5766)

* Fix EffectRackView appearance (GUI).

* Elide the name of the effect when it tends to be too big. (#5752)
* Evenly space the controls (W/D, Decay Gate). (#5750)
* Show the scrollbar in the default theme to close the gap. (#5752)
* Reduce the gap between the effect and the scrollbar. (#5757)
* Use always the same width for the EffectRackview (InstrumentTrack and SampleTrack) to avoid gaps or cutoffs of the background.
* Widen the background in the default theme.
* Widen the embossed space in the background in the classic theme to fit the controls.

* Changes for improving the EffectRackView after reviews.

* Reduce the background for the default theme by 1 pixel.
* Reduce the background for the classic theme by 2 pixels and remove the darker line at the bottom right.
* Reduce the width of long names of the plugin also by 2 pixels.
* Put the controls 2 pixels closer to each other.

include/EffectRackView.h

@@ -46,6 +46,7 @@ public:
 	EffectRackView( EffectChain* model, QWidget* parent = NULL );
 	virtual ~EffectRackView();
 
+	static constexpr int DEFAULT_WIDTH = 245;
 
 public slots:
 	void clearViews();

include/EffectView.h

@@ -57,6 +57,7 @@ public:
 		return castModel<Effect>();
 	}
 
+	static constexpr int DEFAULT_WIDTH = 215;
 
 public slots:
 	void editControls();