fix: escape <textarea value={...}> attribute properly

[baseballyama]

fix: #8429

I think this bug is added in #5701

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[Conduitry]

Is this the right fix? Since we're serializing the value= attribute as the actual content of the <textarea> element, can we instead somehow get it to run through the content escaper rather than the attribute escaper (which would then automatically include < in the things to be escaped)?

[baseballyama]

Is this the right fix? Since we're serializing the value= attribute as the actual content of the <textarea> element, can we instead somehow get it to run through the content escaper rather than the attribute escaper (which would then automatically include < in the things to be escaped)?

OK. makes sense. I updated!

[Uzume]

Can this now be reverted in light of #12989 which reintroduced HTML entity escaping of < for attributes across the board (since being removed in #5701)?