[bhess]

Adds NIST round 3 candidate SQIsign:

• https://sqisign.org/spec
• https://github.com/SQISign/the-sqisign

Integrated using copy_from_upstream.
The code is self-contained, using SHAKE from liboqs common code.

TODOs:

• Currently points to a staging-repo with some modifications to support all liboqs builds. Move to the upstream repo once those changes are integrated.
• Create -tracker branch in oqs-provider

Closes #1946

• Does this PR change the input/output behaviour of a cryptographic algorithm (i.e., does it change known answer test values)? (If so, a version bump will be required from x.y.z to x.(y+1).0.)
• Does this PR change the list of algorithms available -- either adding, removing, or renaming? Does this PR otherwise change an API? (If so, PRs in fully supported downstream projects dependent on these, i.e., oqs-provider will also need to be ready for review and merge by the time this is merged. Also, make sure to update the list of algorithms in the continuous benchmarking files: .github/workflows/kem-bench.yml and sig-bench.yml)

[coveralls]

coverage: 70.281% (-15.0%) from 85.245% — bhe-sqisign into main

[RodriM11]

thank you a lot for this @bhess !

[RodriM11]

As discussed in yesterday's TSC meeting, @xuganyu96 and I will act as reviewers for this PR.