Wg ebpf proxy (#911)

EBPF proxy between TURN (relay) and WireGuard to reduce number of used ports used by the NetBird agent.
- Separate the wg configuration from the proxy logic
- In case if eBPF type proxy has only one single proxy instance
- In case if the eBPF is not supported fallback to the original proxy Implementation

Between the signature of eBPF type proxy and original proxy has 
differences so this is why the factory structure exists

client/internal/engine_test.go

@@ -367,9 +367,9 @@ func TestEngine_UpdateNetworkMap(t *testing.T) {
 					t.Errorf("expecting Engine.peerConns to contain peer %s", p)
 				}
 				expectedAllowedIPs := strings.Join(p.AllowedIps, ",")
-				if conn.GetConf().ProxyConfig.AllowedIps != expectedAllowedIPs {
+				if conn.WgConfig().AllowedIps != expectedAllowedIPs {
 					t.Errorf("expecting peer %s to have AllowedIPs= %s, got %s", p.GetWgPubKey(),
-						expectedAllowedIPs, conn.GetConf().ProxyConfig.AllowedIps)
+						expectedAllowedIPs, conn.WgConfig().AllowedIps)
 				}
 			}
 		})