[client] Use native windows sock opts to avoid routing loops (#4314)

- Move `util/grpc` and `util/net` to `client` so `internal` packages can be accessed
 - Add methods to return the next best interface after the NetBird interface.
- Use `IP_UNICAST_IF` sock opt to force the outgoing interface for the NetBird `net.Dialer` and `net.ListenerConfig` to avoid routing loops. The interface is picked by the new route lookup method.
- Some refactoring to avoid import cycles
- Old behavior is available through `NB_USE_LEGACY_ROUTING=true` env var

client/firewall/iptables/acl_linux.go

@@ -12,7 +12,7 @@ import (
 
 	firewall "github.com/netbirdio/netbird/client/firewall/manager"
 	"github.com/netbirdio/netbird/client/internal/statemanager"
-	nbnet "github.com/netbirdio/netbird/util/net"
+	nbnet "github.com/netbirdio/netbird/client/net"
 )
 
 const (

client/firewall/iptables/router_linux.go

@@ -19,7 +19,7 @@ import (
 	"github.com/netbirdio/netbird/client/internal/routemanager/ipfwdstate"
 	"github.com/netbirdio/netbird/client/internal/routemanager/refcounter"
 	"github.com/netbirdio/netbird/client/internal/statemanager"
-	nbnet "github.com/netbirdio/netbird/util/net"
+	nbnet "github.com/netbirdio/netbird/client/net"
 )
 
 // constants needed to manage and create iptable rules

client/firewall/iptables/router_linux_test.go

@@ -14,7 +14,7 @@ import (
 
 	firewall "github.com/netbirdio/netbird/client/firewall/manager"
 	"github.com/netbirdio/netbird/client/firewall/test"
-	nbnet "github.com/netbirdio/netbird/util/net"
+	nbnet "github.com/netbirdio/netbird/client/net"
 )
 
 func isIptablesSupported() bool {

client/firewall/nftables/acl_linux.go

@@ -16,7 +16,7 @@ import (
 	"golang.org/x/sys/unix"
 
 	firewall "github.com/netbirdio/netbird/client/firewall/manager"
-	nbnet "github.com/netbirdio/netbird/util/net"
+	nbnet "github.com/netbirdio/netbird/client/net"
 )
 
 const (

client/firewall/nftables/router_linux.go

@@ -22,7 +22,7 @@ import (
 	nbid "github.com/netbirdio/netbird/client/internal/acl/id"
 	"github.com/netbirdio/netbird/client/internal/routemanager/ipfwdstate"
 	"github.com/netbirdio/netbird/client/internal/routemanager/refcounter"
-	nbnet "github.com/netbirdio/netbird/util/net"
+	nbnet "github.com/netbirdio/netbird/client/net"
 )
 
 const (