Remove deprecation warning suppression from genpkey

genpkey was supressing deprecation warnings in order to support ENGINE
functionality. We move all of that into a separate file so that we don't
need to suppress the warnings anymore.

Fixes #13118

Reviewed-by: Richard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/13454)

apps/genpkey.c

diff --git a/apps/genpkey.c b/apps/genpkey.c
index 1682c66..d6ab0e6 100644
--- a/apps/genpkey.c
+++ b/apps/genpkey.c
@@ -7,9 +7,6 @@
  * https://www.openssl.org/source/license.html
  */
 
-/* We need to use some engine deprecated APIs */
-#define OPENSSL_SUPPRESS_DEPRECATED
-
 #include <stdio.h>
 #include <string.h>
 #include "apps.h"
@@ -17,9 +14,6 @@
 #include <openssl/pem.h>
 #include <openssl/err.h>
 #include <openssl/evp.h>
-#ifndef OPENSSL_NO_ENGINE
-# include <openssl/engine.h>
-#endif
 
 static int init_keygen_file(EVP_PKEY_CTX **pctx, const char *file, ENGINE *e,
                             OSSL_LIB_CTX *libctx, const char *propq);
@@ -290,8 +284,6 @@
                  OSSL_LIB_CTX *libctx, const char *propq)
 {
     EVP_PKEY_CTX *ctx = NULL;
-    const EVP_PKEY_ASN1_METHOD *ameth;
-    ENGINE *tmpeng = NULL;
     int pkey_id;
 
     if (*pctx) {
@@ -299,29 +291,13 @@
         return 0;
     }
 
-    if (libctx == NULL || e != NULL) {
-        ameth = EVP_PKEY_asn1_find_str(&tmpeng, algname, -1);
-
-#if !defined(OPENSSL_NO_ENGINE) && !defined(OPENSSL_NO_DEPRECATED_3_0)
-        if (ameth == NULL && e != NULL)
-            ameth = ENGINE_get_pkey_asn1_meth_str(e, algname, -1);
-#endif
-        if (ameth == NULL) {
-            BIO_printf(bio_err, "Algorithm %s not found\n", algname);
-            return 0;
-        }
-        ERR_clear_error();
-
-        EVP_PKEY_asn1_get0_info(&pkey_id, NULL, NULL, NULL, NULL, ameth);
-#if !defined(OPENSSL_NO_ENGINE) && !defined(OPENSSL_NO_DEPRECATED_3_0)
-        ENGINE_finish(tmpeng);
-#endif
+    pkey_id = get_legacy_pkey_id(libctx, algname, e);
+    if (pkey_id != NID_undef)
         ctx = EVP_PKEY_CTX_new_id(pkey_id, e);
-    } else {
+    else
         ctx = EVP_PKEY_CTX_new_from_name(libctx, algname, propq);
-    }
 
-    if (!ctx)
+    if (ctx == NULL)
         goto err;
     if (do_param) {
         if (EVP_PKEY_paramgen_init(ctx) <= 0)