Generalise ML-DSA with GYB

[fpseverino]

Generalises the definition of ML-DSA algorithms with GYB to allow the addition of other parameter sets in the future

Checklist

• I've run tests to see all new and existing tests pass
• I've followed the code style of the rest of the project
• I've read the Contribution Guidelines
• I've updated the documentation if necessary

If you've made changes to gyb files

• I've run .script/generate_boilerplate_files_with_gyb and included updated generated files in a commit of this pull request

Motivation:

BoringSSL recently made ML-DSA-87 public in its API, in addition to ML-DSA-65 which has already been integrated into Swift Crypto.
By generating the code with GYB we will be able to add support for ML-DSA-87 very easily in the future when the vendored version of BoringSSL is updated.

Modifications:

Generate the code for MLDSA65 (and in future also for MLDSA87) with GYB.

Result:

Nothing changes in the public API, but adding MLDSA87 in the future will be instantaneous.

[glbrntt]

Thanks for opening this PR. The maintainer of this project is currently out of office so won't get to it for a little while.