vendor: update buildkit to v0.19.0-rc1

Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>

vendor/google.golang.org/grpc/internal/channelz/socket.go

@@ -70,13 +70,18 @@ type EphemeralSocketMetrics struct {
 	RemoteFlowControlWindow int64
 }
 
+// SocketType represents the type of socket.
 type SocketType string
 
+// SocketType can be one of these.
 const (
 	SocketTypeNormal = "NormalSocket"
 	SocketTypeListen = "ListenSocket"
 )
 
+// Socket represents a socket within channelz which includes socket
+// metrics and data related to socket activity and provides methods
+// for managing and interacting with sockets.
 type Socket struct {
 	Entity
 	SocketType       SocketType
@@ -100,6 +105,8 @@ type Socket struct {
 	Security credentials.ChannelzSecurityValue
 }
 
+// String returns a string representation of the Socket, including its parent
+// entity, socket type, and ID.
 func (ls *Socket) String() string {
 	return fmt.Sprintf("%s %s #%d", ls.Parent, ls.SocketType, ls.ID)
 }