test(format/uri): assert IPv6 and IPvFuture host formatting constraints

[AcEKaycgR]

Applies to: draft-v1, draft-04, draft-06, draft-07, draft/2019-09, draft/2020-12

Adds 20 new cases asserting strict syntax constraints on IPv6 and IPvFuture host formats, including square bracket requirements, and Cyrillic/non-ASCII host rejections.

Added:

• Unbracketed IPv6 host (invalid)
• Invalid hex digit in IPv6 brackets (invalid)
• Empty brackets [] host (invalid)
• Brackets in query (invalid)
• Brackets in fragment (invalid)
• Brackets in path (invalid)
• IPv6 with multiple double-colons (invalid)
• IPv6 with 7 groups and no double-colon (invalid)
• IPv6 with 9 groups (invalid)
• IPv6 group with >4 hex digits (invalid)
• IPv6 with out-of-bounds embedded IPv4 octet (invalid)
• Valid IPv6 with embedded IPv4 (valid)
• IPvFuture missing version (invalid)
• IPvFuture missing dot (invalid)
• IPvFuture empty content after dot (invalid)
• IPvFuture with non-hex version (invalid)
• Valid IPvFuture host (valid)
• IPvFuture with uppercase V version (valid)
• Non-ASCII Cyrillic host (invalid)
• Non-ASCII Latin host (invalid)

Ecosystem Impact (Triangulation):

Under Bowtie verification against 8 active implementations, these cases successfully caught live compliance issues:

1. Go Bug Caught: go-gojsonschema incorrectly accepts unbracketed IPv6, empty brackets, brackets in path/query/fragment, and malformed IPv6/IPvFuture hosts.
2. Go Bug Caught: go-gojsonschema incorrectly accepts Cyrillic and non-ASCII Latin characters in host names.
3. PHP Bug Caught: php-opis-json-schema incorrectly rejects valid IPv6 with embedded IPv4 ("http://[::ffff:192.168.1.1]"), valid IPvFuture hosts, and uppercase V versions.
4. PHP Bug Caught: php-opis-json-schema incorrectly accepts brackets in query/fragment.

@jviotti @jdesrosiers @karenetheridge Ready for review.

[jviotti]

Very nice. Looks all correct as far as I can tell and I appreciate the evidence on the ones that break!