slh-dsa: add signature generation tests

slh-dsa: add signature generation tests

This marks the first use of the extended test feature in evp_test.
The reason behind this is the amount of time the full SLH-DSA tests consume.
The non-extended tests chosen so that they exercise all of the algorithms
at least once and all the varying combinations of features for the fast
algorithms.

On my build machine the full test suite takes: 290 seconds.
With the reduction to a dozen tests it takes: 10.5 seconds.

Reviewed-by: Tim Hudson <tjh@openssl.org>
Reviewed-by: Shane Lontis <shane.lontis@oracle.com>
(Merged from https://github.com/openssl/openssl/pull/26750)