Emoji script: infinite loop when image does not load

[iseulde]

Twemoji replaces images that do not load with the original text, which is detected by our mutation observer that parses any added text nodes. If the image never loads there will be an infinite loop.

To fix this we’ll have to look at the removed nodes in the mutation record and return if twemoji is replacing an image with the text in the alt attribute.

[SergeyBiryukov]

Duplicate of #32128.