Update to Mozilla guidelines v5.7

[janbrasna]

Updates to v5.7 from v5.0 (online) and v4.0 (offline), in both cases a breaking change with new cipher list key naming/nesting.

Closes #192 (+also fixes #167)

(This points explicitly to 5.7.json instead of latest.json symlink for better control over releases.)

• Updates JSON parsing.
• Populates old sigalg from data.
• Doesn't fail on missing protocols (NB: e.g. TLSv1.3…) +changes wording around it.
• Fails intermediate on short kex.
• Updates errors to reflect kex size from data.
• Only fails on cipher order for old where relevant.

This doesn't change ordering checks as that may need a separate tweaking (only updated wording to better match reality for now). Also can't really test or enforce modern as that's TLSv1.3-only now, effectively invisible to current cipherscan.