Implement "translate" attribute
This attribute is almost a straightforward enumerated one, but the getter value inherits from parents when the content attribute is absent, even when the parents are non-HTML elements. This initial commit is using LocalName::from on a static string; once html5ever has a release with "translate" in the built-in local name list, a small change will be needed.
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style: sync changes from mozilla-central
See each individual commit for details. This also cherry-picks #23463 with a few fixes that were needed in Gecko-only code.
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Remove unused code (3/N)
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Third PR in a series of PRs to remove unused/dead code from servo, powered by an (upcoming) tool of mine. Please take a look and tell me if you want to keep something.
* First PR: #23477
* Second PR: #23498
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