feat: add parchment layout

[Danielku15]

Issues

Fixes #1987

Proposed changes

Beside some cleanup work this PR adds a new parchment layout which always uses the systems layout from the data model.

The width of the container is still followed and users can fix them manually (e.g. to an A4) by own means.

For the print layout (#1988) in future we will add actual page size information which could become an opt-in (with alternative scaling to fit the viewport?) -> Something for the future.

For the horizontal layout we now always respect and widths configured. As this is a special alphaTex feature, we can safely assume that people want it active when specified.

With this PR we also scale bars relatively to fit them to the page

• during fitting we distributed the "available space" across the bars evenly. e.g. if 4 bars needed 300px, but we had 400px available. every bar got 25px to scale bigger.
• now we relatively scale up the bars which results in a more accurate scaling of the bars regarding their duration.

Checklist

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

Further details

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