In January 2020 Pleroma backend stopped escaping HTML in display names
and passed that responsibility on frontends, compliant with Mastodon's
version of Mastodon API [1]. Pleroma-FE was subsequently modified to
escape the display name [2], however only in the "name_html" field. This
was fine however, since that's what the code rendering display names used.

However, 2 months ago an MR [3] refactoring the way the frontend does emoji
and mention rendering was merged. One of the things it did was moving away
from doing emoji rendering in the entity normalizer and use the unescaped
'user.name' in the rendering code, resulting in HTML injection being
possible again.

This patch escapes 'user.name' as well, as far as I can tell there is no
actual use for an unescaped display name in frontend code, especially
when it comes from MastoAPI, where it is not supposed to be HTML.

[1]: pleroma/pleroma-fe!1052
[2]: pleroma/pleroma!2167
[3]: pleroma/pleroma-fe!1392

handling of broken cases

squash! restructure and tests

to allow scale of "gif" label

Prevents a crash on undefined screen name cases.

become unusable

This seems more intuitive to me and is what I've seen in most other
language pickers.