Fix/ip address and string

[JesusMcCloud]

• Fixes:
  • X509GeneralName.IpAddress now accepts the RFC 5280 §4.2.1.10 name-constraints encoding (address plus subnet mask: 8 octets for IPv4, 32 for IPv6) in addition to bare subjectAltName/issuerAltName addresses (4/16 octets). It previously rejected the 8/32-octet form outright.
  • Asn1String.IA5.isValid now accepts the complete 7-bit IA5 alphabet 0x00–0x7F, including DELETE (0x7F) (ITU-T T.50 / ISO 646); DELETE was previously rejected.
  • Asn1String.UTF8.isValid now reports UTF-8 well-formedness (RFC 3629) via a canonical round-trip instead of testing for the replacement character. A value that legitimately contains U+FFFD is no longer rejected, and malformed/overlong byte sequences are detected reliably.
  • Asn1String.Teletex, Asn1String.General, and Asn1String.Graphic no longer reject legitimate 8-bit or multi-byte content (e.g. Latin-1 or CJK graphic characters). Their true repertoires (ISO 2022 / T.61) cannot be validated exactly, so isValid now performs best-effort recognition: true for a recognized subset, null ("unknown") otherwise, and never false; their String constructors consequently never throw.
    • API change: isValid on these three types widened from Boolean to Boolean? (the base-class type; null denotes "not validated / unknown").
• Other Changes:
  • Document Asn1String repertoires and validation semantics — a per-type table, best-effort/limitation warnings, and X.680 §41 / ITU-T T.50 / RFC 3629 references — in the low-level guide and API docs.

[github-actions]

⚠️⚠️ This pull request targets main. I am re-targeting it to development. ⚠️⚠️

[JesusMcCloud]

rebased manually