Refactor OpenSSL 'RSA' EVP_SIGNATURE to also include RSA+hash composites

Refactor OpenSSL 'RSA' EVP_SIGNATURE to also include RSA+hash composites

(in the code, "sigalg" is used to refer to these composite algorithms,
which is a nod to libcrypto and libssl, where that term is commonly used
for composite algorithms)

To make this implementation possible, wrappers were added around the hash
function itself, allowing the use of existing hash implementations through
their respective OSSL_DISPATCH tables, but also retaining the dynamic fetch
of hash implementations when the digest_sign / digest_verify functionality
is used.  This wrapper allows implementing the RSA+hash composites through
simple initializer function and a custom OSSL_DISPATCH table for each.

Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Neil Horman <nhorman@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/23416)