Allows creation of HashMLDsaSigner that can sign hashes

[harrison314]

Describe your changes

I made modifications that allow you to create a HashMLDsaSigner that can be used to sign an existing hash.

For proper functionality, it is necessary to accept the merge request #654

I added the same option for HashSlhDsaSigner.

My questions

1. Is it necessary to add a check in the static HashMLDsaSigner CreateRawSigner(MLDsaParameters parametersWithoutPrehash, bool deterministic, DerObjectIdentifier preHashOid) method or is there a digest OID for preHashOid?
2. Is it necessary to add a hash length check? I looked at RsaDigestSigner, but I didn't find this check in it.

How has this been tested?

Tested with my own application and with changes in #654

Checklist before requesting a review

• I have performed a self-review of my code
• I have kept the patch limited to only change the parts related to the patch
• This change requires a documentation update

See also Contributing Guidelines.

[peterdettman]

Thanks, @harrison314 . It looks reasonable, though I want to check with bc-java that the approaches are similar.

Some initial changes I'd prefer:

• Use Prehash class instead of NullDigest
• Use name "CreatePrehashSigner" instead of "CreateRawSigner"

[harrison314]

Thanks for the quick response, I've made the required changes.