Use concrete feature names per design spec: "Legacy Address Filter
Fields", "Legacy `strategy` DNS rule action option", "Legacy
`ip_accept_any` DNS rule item", "Legacy `rule_set_ip_cidr_accept_empty`
DNS rule item" for deprecated features, and "Response Match Fields" for
the new response matching section.
Remove all user-facing references to the internal `legacyDNSMode` variable
name. Error messages now reuse the deprecated.Note.MessageWithLink() method
to provide consistent deprecation text with migration URLs. Other internal
jargon ("consume response state", "response_*") is replaced with
user-friendly descriptions.
Add two migration guide entries under 1.14.0: one for strategy → rule items,
one for address filter fields → evaluate with match_response.
