v5.8 major refresh of guidelines

• summary: first major refresh of guidelines since 2020
• remove kDHE ciphers from Intermediate and Old;
  recommended ciphers for Intermediate are now all PFS with AEAD
• change Old dhParamSize from 1024 to 2048 and
  use ffdhe2048 instead of locally generated dhparams
• remove 'go' and 'caddy' cipher list from guidelines;
  instead use IANA cipher names and supportedCiphers list in
  configs.js to filter ciphers supported by Go crypto/tls module
• add PQC hybrid KEM X25519MLKEM768 to recommended tls_curves
  for Modern, Intermediate, and Old configurations