more SubjectDirectoryExtension support

• Changes from 10.8.3 to 10.8.4 (2023-Apr-26)
  • src/asn1x509.js
    • SubjectDirectoryAttributes class
      • add array of array support for arbitrary attribute value
  • src/x509.js
    • add X509.getExtSubjectDirectoryAttributes method for
      ExtSubjectDirectoryAttributes extension
    • update X509.getExtParam method
      • support SubjectDirectoryAttributes
      • parse unknown extension as ASN.1
  • src/base64x.js
    • bugfix foldnl function: when length of s is multiple of n,
      result has unnecessary new line in the end of string.
  • qunit-do-{asn1x509,x509-ext,base64x,x500-param}.html
    • update and add some test cases for above