Extend netbird status command to include health information (#1471)

* Adds management, signal, and relay (STUN/TURN) health probes to the status command.

* Adds a reason when the management or signal connections are disconnected.

* Adds last wireguard handshake and received/sent bytes per peer

client/internal/probe.go

@@ -0,0 +1,51 @@
+package internal
+
+import "context"
+
+// Probe allows to run on-demand callbacks from different code locations.
+// Pass the probe to a receiving and a sending end. The receiving end starts listening
+// to requests with Receive and executes a callback when the sending end requests it
+// by calling Probe.
+type Probe struct {
+	request chan struct{}
+	result  chan bool
+	ready   bool
+}
+
+// NewProbe returns a new initialized probe.
+func NewProbe() *Probe {
+	return &Probe{
+		request: make(chan struct{}),
+		result:  make(chan bool),
+	}
+}
+
+// Probe requests the callback to be run and returns a bool indicating success.
+// It always returns true as long as the receiver is not ready.
+func (p *Probe) Probe() bool {
+	if !p.ready {
+		return true
+	}
+
+	p.request <- struct{}{}
+	return <-p.result
+}
+
+// Receive starts listening for probe requests. On such a request it runs the supplied
+// callback func which must return a bool indicating success.
+// Blocks until the passed context is cancelled.
+func (p *Probe) Receive(ctx context.Context, callback func() bool) {
+	p.ready = true
+	defer func() {
+		p.ready = false
+	}()
+
+	for {
+		select {
+		case <-ctx.Done():
+			return
+		case <-p.request:
+			p.result <- callback()
+		}
+	}
+}