I don't love this solution, but I remember not being able to figure out a way to not specify the max width because it is needed in order for the flowing to work. Without the max-width, the sprite tiles try to be in a row, pushing over everything else.

* refactor LanguageSelector to reuse MenuBarMenu
* localize aria-labels on MenuBar

Fixes integration test which was failing trying to use the context menu

Allows the language selection menu to be active if `?enable=language` is in the URL, otherwise shows a ‘coming soon’ tooltip. This can also land on a branch if we don’t want that available on preview.

- language menu opens if the globe is clicked
- language menu closes if mouse is clicked anywhere outside the language selector
- language list is imported from scratch-l10n
- current locale is updated if another language is selected (i.e. the current language selected changes)

Not in this PR:
- styling of language selector
- actually changing the messages!

Also remove some obsolete code

Pass a `stageSize` property down from a centralized `MediaQuery` in the
GUI component, and control the size of the stage and all surrounding
elements based on that value. Note that this is a pure property and is
not stored in the Redux state, since we gain access to the results of
the media query during `render()` and we shouldn't change Redux state
during `render()`.

Some stage-adjacent elements don't yet react correctly to the smallest
stage size.

This reverts commit 94915a9a.

Also include the hash of the project in load errors from the server so we can debug them

There will probably need to be more backpack config options in the future, so just make this a bit more future proof