DH_check[_params]() use libctx of the dh for prime checks

Reviewed-by: Paul Dale <pauli@openssl.org>
Reviewed-by: Shane Lontis <shane.lontis@oracle.com>
Reviewed-by: Hugo Landau <hlandau@openssl.org>
(Merged from #19656)

(cherry picked from commit 7c639f0)

crypto/dh/dh_check.c

@@ -73,7 +73,7 @@ int DH_check_params(const DH *dh, int *ret)
     BN_CTX *ctx = NULL;
 
     *ret = 0;
-    ctx = BN_CTX_new();
+    ctx = BN_CTX_new_ex(dh->libctx);
     if (ctx == NULL)
         goto err;
     BN_CTX_start(ctx);
@@ -155,7 +155,7 @@ int DH_check(const DH *dh, int *ret)
     if (!DH_check_params(dh, ret))
         return 0;
 
-    ctx = BN_CTX_new();
+    ctx = BN_CTX_new_ex(dh->libctx);
     if (ctx == NULL)
         goto err;
     BN_CTX_start(ctx);