Fix DNS resolution and hostname parsing (getaddrinfo rewrite)

[dwayz94]

Modernize DNS Resolution in netadr_t

This PR replaces the old gethostbyname() logic with a modern getaddrinfo() implementation and improves parsing of host:port strings.

Highlights

• Reliable DNS resolution using getaddrinfo
• Correct handling of domain names and subdomains
• Proper IPv4 and IPv4-mapped IPv6 support
• Stable parsing of example.com:27015 and similar formats

Reason

The previous implementation caused failures when connecting to servers via domain names.
This patch makes hostname resolution consistent and compatible with modern setups.