Add private setters for "from" and "to" (#7071)

* Add private setters for "from" and "to"

Add private setters for the "from" and "to" values in `AudioFileProcessorWaveView`. When being used the setters will ensure that the bounds are respected.

Also add a `range` method because this computation was done repeatedly throughout the code.

Fixes #7068 but masks some of the original problems with the code that computes out-of-bounds values for "from" and "to" like the `slide` method. Problematic code can still be found by temporarily adding the following assertions to the setters:
* `assert (to <= m_sample->sampleSize());` in `setTo`
* `assert (from >= 0);` in `setFrom`

* Remove superfluous calls to qMax and qMin

plugins/AudioFileProcessor/AudioFileProcessorWaveView.h

@@ -152,6 +152,9 @@ public:
 
 	void updateSampleRange();
 private:
+	void setTo(f_cnt_t to);
+	void setFrom(f_cnt_t from);
+	f_cnt_t range() const;
 	void zoom(const bool out = false);
 	void slide(int px);
 	void slideSamplePointByPx(Point point, int px);