Add SLH_DSA to the FIPS provider.

Add SLH_DSA to the FIPS provider.

The keygen tests required "entropy" to be added via an additional
parameter for ACVP testing. This is required because TEST_RAND cant be
used to pass entropy to the FIPS provider, due to it not knowing the
lib ctx of the FIPS provider.

Reviewed-by: Paul Dale <ppzgs1@gmail.com>
Reviewed-by: Viktor Dukhovni <viktor@openssl.org>
Reviewed-by: Tim Hudson <tjh@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/25882)