Remove ENABLE_DILITHIUM flag

[jakemas]

Issues:

It's time. (also we need to do this to add ML-DSA to the FIPS module)

Description of changes:

• Removed the enable_dilithium flag
• Added an experimental flag (based on the deprecated flag) to indicate the external APIs may still be subject to change as the standards space develops.
• Renamed EVP_PKEY_pqdsa_new_raw_private_key to EVP_PKEY_pqdsa_new_raw_secret_key to better match the equivalent API for KEMs (EVP_PKEY_kem_new_raw_secret_key).

Call-outs:

Removing the flag has little consequence -- other than it makes the APIs we expose in include/openssl/evp.h that much more "final". We should consider how much we like them before we commit to them. We made a point to refer to asymmetric keypairs as public and private keys, rather than public and secret keys. However, we haven't always been consistant with this, so there is a mix of both in the library. Users will find the consistency between EVP_PKEY_pqdsa_new_raw_secret_key and EVP_PKEY_kem_new_raw_secret_key more satisfying.

Once we are happy with the name, including the decision around PQDSA, then we can remove the experimental flags. Personally, I'd advocate for NISTDSA as all NIST signature schemes are matching these API conventions (sign, pre-hash-sign, context-sign -- see ed25519, ML-DSA, SLH-DSA, FN-DSA as examples). Most of this naming is internal, with the exception of the three external functions: EVP_PKEY_CTX_pqdsa_set_params, EVP_PKEY_pqdsa_new_raw_secret_key, EVP_PKEY_pqdsa_new_raw_public_key.

Testing:

To celebrate the removal of this flag, enjoy this haiku:

feature flag removed,
post-quantum strength stands alone,
simpler code prevails.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license and the ISC license.

[jakemas]

Alternative option is that we place the three APIs in a new file within https://github.com/aws/aws-lc/tree/main/include/openssl/experimental. Open to thoughts from the team.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 98.00000% with 2 lines in your changes missing coverage. Please review.

Project coverage is 78.92%. Comparing base (f45bc34) to head (4c6b994).

Files with missing lines	Patch %	Lines
...o/dilithium/pqcrystals_dilithium_ref_common/poly.c	96.66%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2070      +/-   ##
==========================================
+ Coverage   78.76%   78.92%   +0.15%     
==========================================
  Files         598      610      +12     
  Lines      103747   105266    +1519     
  Branches    14735    14921     +186     
==========================================
+ Hits        81718    83076    +1358     
- Misses      21375    21539     +164     
+ Partials      654      651       -3     

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[jakemas]

will merge #2072 first to split this PR into smaller sized additions

[jakemas]

Seems to be multiple definitions of crypto_sign_keypair and crypto_sign_open when integration testing against libmariadb who seem to use the same names for their ed25519 implementation. Addressed in #2072