Changes to rendering of pedal symbols and ottava

[XiaoMigros]

Resolves: #17885

Pedal symbols now render through the musical symbols font, and so does the end text for ottavas.
The pedal continue text default now uses pedal parentheses instead of text parentheses.
Perhaps the pedal font size should be 10pt by default?

[its-not-nice]

All music symbols should have a nominal size of 20pt (which follows stave size).

The text size for pedal lines should indeed be 10pt by default - I think the current 12pt was a kludge to get the symbols looking sort-of-okay in scale - but ideally that should only affect plain text used in these contexts (that goes for ottavas too, actually, and anywhere else), but that raises the question of how to manage sizing of these two types of text separately. Music symbols should be sized with a % scale, and normal text set in points, as is currently; changing one shouldn't affect the other. Perhaps it's enough to have a 'Music symbol scale' (or similar) field added to the relevant text styles for now? (See my comment to the tuplets PR)

[XiaoMigros]

The changes made in this PR have been incorporated into #20772.