refactor: move ErrorWrapperTLSHandshaker to errorsx (#418)

Part of https://github.com/ooni/probe/issues/1505

internal/errorsx/tls.go

@@ -0,0 +1,31 @@
+package errorsx
+
+import (
+	"context"
+	"crypto/tls"
+	"net"
+)
+
+// TLSHandshaker is the generic TLS handshaker
+type TLSHandshaker interface {
+	Handshake(ctx context.Context, conn net.Conn, config *tls.Config) (
+		net.Conn, tls.ConnectionState, error)
+}
+
+// ErrorWrapperTLSHandshaker wraps the returned error to be an OONI error
+type ErrorWrapperTLSHandshaker struct {
+	TLSHandshaker
+}
+
+// Handshake implements TLSHandshaker.Handshake
+func (h *ErrorWrapperTLSHandshaker) Handshake(
+	ctx context.Context, conn net.Conn, config *tls.Config,
+) (net.Conn, tls.ConnectionState, error) {
+	tlsconn, state, err := h.TLSHandshaker.Handshake(ctx, conn, config)
+	err = SafeErrWrapperBuilder{
+		Classifier: ClassifyTLSFailure,
+		Error:      err,
+		Operation:  TLSHandshakeOperation,
+	}.MaybeBuild()
+	return tlsconn, state, err
+}