Replace use of `list` to parse array keys into variables. `list` throws errors if the keys don't exist, and many extenders will not define the new array keys. The code path already falls back effectively for empty values.
Also add translator comments to screen reader hidden text, fix a docblock, and fix an HTML error.
Follow up to [r55971].
Props kebbet, chouby, joedolson.
Fixes#32170.
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