Implement UAX 50 to allow Vertical Mixed layout of text.

Prerequisites

[x] I have written a descriptive pull-request title
[x] I have verified that there are no overlapping pull-requests open
[x] I have verified that I am following matches the existing coding patterns and practice as demonstrated in the repository. These follow strict Stylecop rules :cop:.
[x] I have provided test coverage for my change (where applicable)

Description

Provides an implementation of Unicode Standard Annex #50 Unicode Vertical Text Layout

There's a lot going on here.

Introduced two new layout modes - LayoutMode.VerticalMixedLeftRight and LayoutMode.VerticalMixedRightLeft
Split global FontMetrics properties into separate HorizontalMetrics and VerticalMetrics types since they can be different.
Added support to CodePoint for the detection of a new VerticalOrientationType that provides guidance to how the glyph should be laid out.
Updated the shaping process to reposition glyphs based upon those values.
Updated the method to render decorations to use the correct metrics and handle vertical or horizontal lines.
Fixed an issue where text lines were broken incorrectly
Fixed vertical layout to use the vertical decorations.
Added relevant tests.

Here's some of the output.

Note. I performed various comparisons across different browsers and Microsoft Word. As expected, they all had their own slight twist on where exactly the decorators should be rendered for vertical fonts. It seems the ones in the font themselves are ignored. I based my implementation on the Chromium implementation however I am using the horizontal metrics for rotated horizontal fonts as they are still correctly relative to the baseline.

I had to do a local update to ImageSharp.Drawing to update the renderers there to handle vertical decorators but I will do a follow up PR to handle that.

Mixed English and Japanese using Segoi UI and Microsoft YaHei (TTF)

Japanese 日本語 Japanese 日本語 Japanese 日本語 Japanese 日本語 Japanese 日本語 Japanese 日本語 Japanese 日本語 Japanese

Mixed English and Emoji using Segoe UI and Segoe UI Emoji

The quick👩🏽‍🚒 brown fox jumps over the lazy dog

Mixed English and Japanese using Source Sans ProI and Microsoft YaHei (CFF)

Japanese 日本語 Japanese 日本語 Japanese 日本語 Japanese 日本語 Japanese 日本語 Japanese 日本語 Japanese 日本語 Japanese

Codecov Report

Merging #327 (33186a2) into main (2a7c8a9) will decrease coverage by 1%. The diff coverage is 72%.

@@          Coverage Diff           @@
##            main    #327    +/-   ##
======================================
- Coverage     83%     83%    -1%     
======================================
  Files        224     227     +3     
  Lines      12437   12838   +401     
  Branches    1792    1844    +52     
======================================
+ Hits       10420   10734   +314     
- Misses      1597    1663    +66     
- Partials     420     441    +21

Flag	Coverage Δ
unittests	`83% <72%> (-1%)`	:arrow_down:

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
src/SixLabors.Fonts/FontMetrics.cs	`100% <ø> (ø)`
src/SixLabors.Fonts/FontRectangle.cs	`95% <ø> (+5%)`	:arrow_up:
src/SixLabors.Fonts/Glyph.cs	`100% <ø> (ø)`
...nts/Tables/AdvancedTypographic/GPos/AnchorTable.cs	`33% <0%> (-2%)`	:arrow_down:
src/SixLabors.Fonts/TextRenderer.cs	`100% <ø> (ø)`
...ode/Resources/VerticalOrientationTrie.Generated.cs	`100% <ø> (ø)`
src/SixLabors.Fonts/GlyphMetrics.cs	`60% <13%> (-13%)`	:arrow_down:
src/SixLabors.Fonts/Font.cs	`53% <33%> (-1%)`	:arrow_down:
...bors.Fonts/Tables/AdvancedTypographic/GPosTable.cs	`84% <50%> (+<1%)`	:arrow_up:
src/SixLabors.Fonts/GlyphRendererParameters.cs	`60% <60%> (+1%)`	:arrow_up:
... and 24 more

... and 1 file with indirect coverage changes

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SixLabors / Fonts