Add style options for 'String tunings' element

Problem to be solved

The circled numbers in the 'String tunings' and 'String number' elements cannot easily be made to look the same.

The 'String tunings' element does not allow for customization of the number's font (likely because they are SMuFL unicode characters, not a custom-rendered number with a circle drawn around it), the syntax (it's always a number followed by an en dash followed by the note name), or the row/column layout of the strings. You can change the font of the en dash and note name in 'Styles > Text styles > String tunings' but it does not affect the circled number.

The font 'String number' elements (the individual numbers with circles applied to notes) does not match the

Task

A new Style dialog page is needed for customizing bother 'String tunings' and 'String number' elements.

String tunings:

• Allow changing the style of the unicode circled numbers in the 'String tunings' element to be drawn like we draw the 'String numbers' element

  • We could then apply the existing 'String numbers' text style to the number within this element

• Allow other syntaxes, like '6 to D', '6 = D', and maybe a user-defined option (suggested by @rgreen5 in https://github.com/musescore/MuseScore/issues/20784)

• Scale

• Spacing: to the staff; between columns/rows; between the number, dash, and note name

String numbers:

• Allow using the unicode characters for the 'String numbers' elements instead of choosing a custom font
• Scale
• Spacing to staff