chore!(amneziawg): refactor to be separate from wireguard

- amneziawg is now a VPN protocol and no longer a Wireguard implementation
- Use it with VPN_TYPE=amneziawg
- document AMNEZIAWG_* options in Dockerfile
- document amneziawg support in readme
- separate amneziawg settings and code from wireguard
- re-use code from wireguard whenever possible

internal/amneziawg/netlinker.go

@@ -0,0 +1,36 @@
+package amneziawg
+
+import (
+	"net/netip"
+
+	"github.com/qdm12/gluetun/internal/netlink"
+)
+
+//go:generate mockgen -destination=netlinker_mock_test.go -package amneziawg . NetLinker
+
+type NetLinker interface {
+	AddrReplace(linkIndex uint32, addr netip.Prefix) error
+	Router
+	Ruler
+	Linker
+	IsWireguardSupported() (ok bool, err error)
+}
+
+type Router interface {
+	RouteList(family uint8) (routes []netlink.Route, err error)
+	RouteAdd(route netlink.Route) error
+}
+
+type Ruler interface {
+	RuleAdd(rule netlink.Rule) error
+	RuleDel(rule netlink.Rule) error
+}
+
+type Linker interface {
+	LinkAdd(link netlink.Link) (linkIndex uint32, err error)
+	LinkList() (links []netlink.Link, err error)
+	LinkByName(name string) (link netlink.Link, err error)
+	LinkSetUp(linkIndex uint32) error
+	LinkSetDown(linkIndex uint32) error
+	LinkDel(linkIndex uint32) error
+}