crypto: always return certificate serial numbers as uppercase

This hides a discrepancy between OpenSSL and BoringSSL, as
the latter returns lowercase hex values.

Refs: #61459 (comment)
PR-URL: #61752
Reviewed-By: Shelley Vohr <shelley.vohr@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Tim Perry <pimterry@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>

Author: addaleax

src/crypto/crypto_x509.cc

@@ -253,8 +253,8 @@ MaybeLocal<Value> GetSignatureAlgorithmOID(Environment* env,
 
 MaybeLocal<Value> GetSerialNumber(Environment* env, const X509View& view) {
   if (auto serial = view.getSerialNumber()) {
-    return OneByteString(env->isolate(),
-                         static_cast<unsigned char*>(serial.get()));
+    return ToV8Value(
+        env, ToUpper(std::string_view(static_cast<char*>(serial.get()))));
   }
   return Undefined(env->isolate());
 }