reactions: Label text can linebreak sooner than necessary

[chrisbobbe]

In a reaction chip in the message list (#410), the label with users' names (seen with UserSettings.displayEmojiReactionUsers) can get linebreaked for text wrapping sooner than is necessary:

In this example, it says:

Cordelia, Lear's daughter, You,
Polonius

when there is actually enough room to say

Cordelia, Lear's daughter, You, Polonius

This is a tradeoff we made consciously when implementing a reasonable layout for text emoji (where the button looks like ":tada: You, Polonius" instead of "🎉 You, Polonius"), when both the emoji text and the reaction label are long. See the first two pairs of screenshots at #410 (comment), which highlight the upside of that tradeoff. If we were less careful about text emoji, they could look extremely broken.

If we decide that the current issue is worth fixing, we should try to fix it without breaking text emoji. And we should keep in mind that UserSettings.emojiset isn't enough to determine whether we're going to show a text emoji, because we show text emoji for various error conditions, including when an image emoji fails to load (which we learn about especially late).