Change cipher suite alert for 0 length cipher_suites

From RFC 8446:

Note: TLS defines two generic alerts (see Section 6) to use upon
   failure to parse a message.  Peers which receive a message which
   cannot be parsed according to the syntax (e.g., have a length
   extending beyond the message boundary or contain an out-of-range
   length) MUST terminate the connection with a "decode_error" alert.
   Peers which receive a message which is syntactically correct but
   semantically invalid (e.g., a DHE share of p - 1, or an invalid enum)
   MUST terminate the connection with an "illegal_parameter" alert.

A zero length cipher suite list I think is considered out of range, and
so we should return "decode_error" rather than "illegal_parameter"

Fixes #25309

Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Saša Nedvědický <sashan@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/26781)

(cherry picked from commit 2ce46ad8ce)

ssl/ssl_lib.c

@@ -6833,7 +6833,7 @@ int ssl_cache_cipherlist(SSL_CONNECTION *s, PACKET *cipher_suites, int sslv2form
     n = sslv2format ? SSLV2_CIPHER_LEN : TLS_CIPHER_LEN;
 
     if (PACKET_remaining(cipher_suites) == 0) {
-        SSLfatal(s, SSL_AD_ILLEGAL_PARAMETER, SSL_R_NO_CIPHERS_SPECIFIED);
+        SSLfatal(s, SSL_AD_DECODE_ERROR, SSL_R_NO_CIPHERS_SPECIFIED);
         return 0;
     }