chore(netlink): separate linux only and OS independent code

- Move `Addr` and its `String` method to `types.go`
- Move `IsWireguardSupported` to `wireguard.go` to have `family.go` OS independant
- Remove dependency on vishvananda/netlink in `ipv6.go`
- Move `Link` to `types.go`
- Move `Route` to `types.go`
- Move `Rule` and its `String` method to `types.go`

internal/netlink/link.go

@@ -2,14 +2,6 @@ package netlink
 
 import "github.com/vishvananda/netlink"
 
-type Link struct {
-	Type      string
-	Name      string
-	Index     int
-	EncapType string
-	MTU       uint16
-}
-
 func (n *NetLink) LinkList() (links []Link, err error) {
 	netlinkLinks, err := netlink.LinkList()
 	if err != nil {