Toolbox buttons break modmail sidebar

[eritbh]

A recent change to the user info sidebar in modmail means that the position where Toolbox inserts the user info buttons now results in broken display.

The user info no longer scrolls, only the tabs beneath do, so we have limited vertical space to work with. We probably want to reduce our buttons back down to the single-letter labels and insert them underneath the username (.ModIdCard__UserNameMetaData) or profile link (.ModIdCard__UserProfileLink). We can also steal one of those classes to get text centering for free, to match up with the rest of the display.

[eritbh]

Reddit has reverted this sidebar change for now, so it's not something we need to address immediately for v6.