Adjust grace positioning to utilize free space

[Danielku15]

Issues

Fixes #1093

Proposed changes

1. Ensures we uniquely store beat sizes in the BarLayoutingInfo by utilizing the id instead of index.
2. Utilize the PreBeatSize of the Beat after the grace notes to compute the position of the grace notes allowing them to be placed closer to the note if the space is unused.
3. Ensure the ScoreBrushGlyph doesn't consume any space if nothing is rendered

Checklist

• I consent that this change becomes part of alphaTab under it's current or any future open source license
• Changes are implemented
• Existing builds tests pass
• New tests were added

Further details

• This is a breaking change
• This change will require update of the documentation/website

[goodgame365]

Great, thank you very much！