Validate IP-like hosts in UriAttribute and extend test coverage

[davidkallesen]

Summary

Uri.TryCreate accepts malformed IP addresses like 1231.0.0.1 by misclassifying them as DNS hostnames. This PR adds host validation to UriAttribute.IsValid that detects hosts consisting solely of digits and dots (IP-like) but not recognized as valid IPv4, and rejects them. It also significantly extends test coverage for IPAddressAttribute, UriAttribute, and the URI string extension methods.

Changes

🐛 Fixes

• Reject URIs with malformed IP-like hosts (e.g. opc.tcp://1231.0.0.1:4840, http://999.999.999.999:8080) that Uri.TryCreate
  incorrectly accepts as DNS names

✅ Tests

• Extend IPAddressAttributeTests with comprehensive IPv4/IPv6 coverage, edge cases, required/optional, and TryIsValid with
  attribute overload
• Add invalid IP host and valid IP host test cases across UriAttributeTests for IsValid, TryIsValid, IsValidHttpOrHttps,
  TryIsValidHttpOrHttps, IsValidOpcTcp, and TryIsValidOpcTcp
• Add port boundary test cases (0, 65535, 65536) documenting that out-of-range ports are correctly rejected
• Add IP and port test cases to StringHasIsExtensionsTests for IsUri, IsUriHttpOrHttps, and IsUriOpcTcp

📝 Documentation

• Add XML documentation to the private IsHostValid helper explaining the detection strategy