[client] Sweep connections on network loss via a shared netevents manager (#7254)

Losing the last network only flipped the availability state: the dead management, signal and relay sockets stayed silently connected until their own timeouts, so the client kept reporting Connected with no network at all.

Introduce client/netevents with a Manager that ties the availability state, the connection sweeper and the status recorder together, and move the netstate and netsweep packages under it (netsweep renamed to sweep). SetNetworkAvailable(false) now also sweeps the registered connections so their owners redial and the listener reaches the NoNetwork state.

The Android and iOS bindings own a Manager instance and inject it through the constructors; consumers hold the concrete *Manager whose nil zero value reports always-online and never sweeps, with interfaces kept only as parameter contracts. The relay guard settle wait moved into the Manager as WaitSettled, removing the netevents import from the relay package.

client/internal/engine.go

@@ -59,7 +59,7 @@ import (
 	"github.com/netbirdio/netbird/client/internal/syncstore"
 	"github.com/netbirdio/netbird/client/internal/updater"
 	"github.com/netbirdio/netbird/client/jobexec"
-	"github.com/netbirdio/netbird/client/netstate"
+	"github.com/netbirdio/netbird/client/netevents"
 	cProto "github.com/netbirdio/netbird/client/proto"
 	"github.com/netbirdio/netbird/client/system"
 	nbdns "github.com/netbirdio/netbird/dns"
@@ -182,9 +182,9 @@ type EngineServices struct {
 	UpdateManager  *updater.Manager
 	ClientMetrics  *metrics.ClientMetrics
 	MetricsCtx     context.Context
-	// NetState gates the reconnection loops on OS-reported network
+	// NetMgr gates the reconnection loops on OS-reported network
 	// availability; nil disables gating.
-	NetState *netstate.State
+	NetMgr *netevents.Manager
 }
 
 // Engine is a mechanism responsible for reacting on Signal and Management stream events and managing connections to the remote peers.
@@ -208,9 +208,9 @@ type Engine struct {
 	config    *EngineConfig
 	mobileDep MobileDependency
 
-	// netState gates the peer reconnection guards on OS-reported network
+	// netMgr gates the peer reconnection guards on OS-reported network
 	// availability; nil disables gating.
-	netState *netstate.State
+	netMgr *netevents.Manager
 
 	// STUNs is a list of STUN servers used by ICE
 	STUNs []*stun.URI
@@ -345,7 +345,7 @@ func NewEngine(
 		syncMsgMux:         &sync.Mutex{},
 		config:             config,
 		mobileDep:          mobileDep,
-		netState:           services.NetState,
+		netMgr:             services.NetMgr,
 		STUNs:              []*stun.URI{},
 		TURNs:              []*stun.URI{},
 		networkSerial:      0,
@@ -1902,8 +1902,8 @@ func (e *Engine) createPeerConn(pubKey string, allowedIPs []netip.Prefix, agentV
 			Addr:           e.getRosenpassAddr(),
 			PermissiveMode: e.config.RosenpassPermissive,
 		},
-		ICEConfig:    e.createICEConfig(),
-		NetworkState: e.netState,
+		ICEConfig: e.createICEConfig(),
+		NetMgr:    e.netMgr,
 	}
 
 	serviceDependencies := peer.ServiceDependencies{