Sort translations after filtering them out.

[fnando]

PR Checklist

PR Structure

• This PR has reasonably narrow scope (if not, break it down into smaller
  PRs).
• This PR avoids mixing refactoring changes with feature changes (split into
  two PRs otherwise).
• This PR's title starts is concise and descriptive.

Thoroughness

• This PR adds tests for the most critical parts of the new functionality or
  fixes.
• I've updated any docs, .md files, etc… affected by this change.

What

Deep sort translations after filtering them out.

Why

This is one of the advertised features of v4, but turns I never actually implemented it.

Close #691.

Known limitations

Given this is a built-in behaviour, it can't be disabled nor replaced.