Backport Bugzilla 1666613: Display XML error pages in the browser directionality while force LTRing the XML code itself, without the use of intl.css

⬅️ Backport Patchset

Bookkeeping

Issue(s)

• tor-browser#xxxxx
• mullvad-browser#xyz
• https://bugzilla.mozilla.org/show_bug.cgi?id=1666613

Merge Request(s)

• tor-browser!xxxx
• Upstream commit: 49afdd3f

Target Channels

• Alpha (alpha already contains this patch)
• Stable
• Legacy

Notes

This is needed to possibly make intl.css unavailable to content.

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