pool: add GetInstances method, that returns current instances connections state

The GetConnections method has been added, which is necessary to monitor the current state of the pool. This should help implement dynamic tracking of tarantool topology changes.

Author: maksim.konovalov

Diff for: pool/connection_pool.go

@@ -1506,3 +1506,24 @@ func isFeatureInSlice(expected iproto.Feature, actualSlice []iproto.Feature) boo
 	}
 	return false
 }
+
+// GetInstances retrieves a slice of Instance objects representing the connections in the pool.
+func (p *ConnectionPool) GetInstances() []Instance {
+	p.endsMutex.Lock()
+	defer p.endsMutex.Unlock()
+
+	res := make([]Instance, 0, len(p.ends))
+
+	i := 0
+
+	for _, end := range p.ends {
+		res[i] = Instance{
+			Name:   end.name,
+			Dialer: end.dialer,
+			Opts:   end.opts,
+		}
+		i++
+	}
+
+	return res
+}