chore(netlink): define own types with minimal fields

- Allow to swap `github.com/vishvananda/netlink`
- Allow to add build tags for each platform
- One step closer to development on non-Linux platforms

internal/routing/conversion.go

@@ -6,34 +6,6 @@ import (
 	"net/netip"
 )
 
-func NetipPrefixToIPNet(prefix *netip.Prefix) (ipNet *net.IPNet) {
-	if prefix == nil {
-		return nil
-	}
-
-	s := prefix.String()
-	ip, ipNet, err := net.ParseCIDR(s)
-	if err != nil {
-		panic(err)
-	}
-	ipNet.IP = ip
-	return ipNet
-}
-
-func netIPNetToNetipPrefix(ipNet net.IPNet) (prefix netip.Prefix) {
-	if len(ipNet.IP) != net.IPv4len && len(ipNet.IP) != net.IPv6len {
-		return prefix
-	}
-	var ip netip.Addr
-	if ipv4 := ipNet.IP.To4(); ipv4 != nil {
-		ip = netip.AddrFrom4([4]byte(ipv4))
-	} else {
-		ip = netip.AddrFrom16([16]byte(ipNet.IP))
-	}
-	bits, _ := ipNet.Mask.Size()
-	return netip.PrefixFrom(ip, bits)
-}
-
 func netIPToNetipAddress(ip net.IP) (address netip.Addr) {
 	address, ok := netip.AddrFromSlice(ip)
 	if !ok {