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/types.go

@@ -0,0 +1,58 @@
+package netlink
+
+import (
+	"fmt"
+	"net/netip"
+)
+
+type Addr struct {
+	Network netip.Prefix
+}
+
+func (a Addr) String() string {
+	return a.Network.String()
+}
+
+type Link struct {
+	Type      string
+	Name      string
+	Index     int
+	EncapType string
+	MTU       uint16
+}
+
+type Route struct {
+	LinkIndex int
+	Dst       netip.Prefix
+	Src       netip.Addr
+	Gw        netip.Addr
+	Priority  int
+	Family    int
+	Table     int
+	Type      int
+}
+
+type Rule struct {
+	Priority int
+	Family   int
+	Table    int
+	Mark     int
+	Src      netip.Prefix
+	Dst      netip.Prefix
+	Invert   bool
+}
+
+func (r Rule) String() string {
+	from := "all"
+	if r.Src.IsValid() {
+		from = r.Src.String()
+	}
+
+	to := "all"
+	if r.Dst.IsValid() {
+		to = r.Dst.String()
+	}
+
+	return fmt.Sprintf("ip rule %d: from %s to %s table %d",
+		r.Priority, from, to, r.Table)
+}