speed: Increase MAX_SIG_NUM and fix its usage in loopargs_t fields

speed: Increase MAX_SIG_NUM and fix its usage in loopargs_t fields

Increase the maximum number of signature algorithms.

With the introduction of the SignMessage and VerifyMessage API with
OpenSSL 3.4 the providers that support combined digest and sign algorithms
register quite a lot more signature algorithms, so the current limit of
111 is hit easily.

While at it correct the definitions of the signature fields within the
loopargs_t structure to use MAX_SIG_NUM instead of MAX_KEM_NUM.

Closes: https://github.com/openssl/openssl/issues/27873
Signed-off-by: Ingo Franzki <ifranzki@linux.ibm.com>
Reviewed-by: Neil Horman <nhorman@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Paul Dale <ppzgs1@gmail.com>
(Merged from https://github.com/openssl/openssl/pull/27878)