Simplify Falcon DSA using fork of fn-dsa

[Al-Kindi-0]

Describe your changes

Context #774 (comment)

Checklist before requesting a review

• Repo forked and branch created from next according to naming convention.
• Commit messages and codestyle follow conventions.
• Relevant issues are linked in the PR description.
• Tests added for new functionality.
• Documentation/comments updated according to changes.

[bobbinth]

Question (and without having looked at the code): what is the relationship of this PR to #774?

[Al-Kindi-0]

Question (and without having looked at the code): what is the relationship of this PR to #774?

This is just one of a few proposals at integrating fn-dsa into our Falcon implementation. The discussion here provides more context, but to summarize, the current PR uses a minimal fork of fn-dsa instead of moving the code for signing to miden-crypto. Both approaches have their merits and the aforementioned discussion is still trying to find the best one.

[Al-Kindi-0]

Superseded by #796