pkey: use EVP_PKEY_CTX_new_from_name() on OpenSSL 3.0

Replace EVP_PKEY_CTX_new_id() with the new EVP_PKEY_CTX_new_from_name()
which takes the algorithm name in a string instead of in an NID.

Author: rhenium

ext/openssl/ossl_pkey.c

@@ -316,6 +316,11 @@ pkey_generate(int argc, VALUE *argv, VALUE self, int genparam)
             ossl_raise(ePKeyError, "EVP_PKEY_CTX_new");
     }
     else {
+#if OSSL_OPENSSL_PREREQ(3, 0, 0)
+        ctx = EVP_PKEY_CTX_new_from_name(NULL, StringValueCStr(alg), NULL);
+        if (!ctx)
+            ossl_raise(ePKeyError, "EVP_PKEY_CTX_new_from_name");
+#else
         const EVP_PKEY_ASN1_METHOD *ameth;
         ENGINE *tmpeng;
         int pkey_id;
@@ -334,6 +339,7 @@ pkey_generate(int argc, VALUE *argv, VALUE self, int genparam)
         ctx = EVP_PKEY_CTX_new_id(pkey_id, NULL/* engine */);
         if (!ctx)
             ossl_raise(ePKeyError, "EVP_PKEY_CTX_new_id");
+#endif
     }
 
     if (genparam && EVP_PKEY_paramgen_init(ctx) <= 0) {