po: Update translations from downstream in Endless

We’ll drop the Transifex translation machinery downstream after this, so this is the last time the translations will be synced.

I have not verified any of these translations, but am upstreaming them on the premise that some strings are better than no strings.

This commit was produced by:

1. ninja malcontent-update-po
2. Copy in po files from downstream
3. ninja malcontent-update-po again
4. Manually drop header-only changes
5. Manually drop changes to translator-credits
6. Manually drop some conflicted strings from id.po (prefer the upstream versions)
7. Manually merge headers

There are no more help/ translations to upstream.

Signed-off-by: Philip Withnall withnall@endlessm.com