refactor(tests): harmonize crypto test data and improve test quality

refactor(tests): harmonize crypto test data and improve test quality

- Reorganize OCPP20CertificateTestData: move CA/leaf certificates into
  Real X.509 section, simplify JSDoc to consistent one-line format
- Add round-trip tests (derLength → readDerLength) replacing duplicate
  raw byte assertions
- Add semantic test for extractDerIssuer (DER hash vs string DN hash)
- Replace eslint-disable || workaround with assert.match regex
- Update Asn1DerUtils @description to cover parsing functions