Bug 1726580 [wpt PR 30087] - [mathml] Implement font-family: math and use it for...

Bug 1726580 [wpt PR 30087] - [mathml] Implement font-family: math and use it for <math> tags., a=testonly

Automatic update from web-platform-tests
[mathml] Implement font-family: math and use it for <math> tags.

This CL implements the generic font family name "math" [1] and use
it as the default family for MathML <math> tags in the UA stylesheet
[2]. This is done under a new CSSFontFamilyMath experimental feature
implied by the MathMLCore one. This CL only introduces core logic,
with the expectation that it will be refined later:

- font-family: math is not used to pick a math font on Android since
  no font with an OpenType table are pre-installed [3].

- font-family: math just use the hardcoded "Latin Modern Math" font
  on other platforms. They should be configurable by the users.

Intent to prototype is [4].

[1] https://www.w3.org/TR/css-fonts-4/#valdef-font-family-math
[2] https://w3c.github.io/mathml-core/#the-top-level-math-element
[3] https://github.com/googlefonts/noto-fonts/issues/330
[4] https://groups.google.com/a/chromium.org/g/blink-dev/c/CnQuMzqabqE/m/WlZfKOSpAAAJ

Bugs: 6606, 1228189
Change-Id: I546de83520c74df593260f35f670c076ba774872
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2119534
Reviewed-by: Dominik Röttsches <drott@chromium.org>
Commit-Queue: Frédéric Wang <fwang@igalia.com>
Cr-Commit-Position: refs/heads/main@{#914708}

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wpt-commits: 755037a1db0cbb0958f59c5137207bb530bebd23
wpt-pr: 30087