Update HQC to conform with the latest submission: see https://pqc-hqc.org. This also removes the avx2 optimized version of HQC, as it is not interoperable with the latest standard and renames HQC-RMRS to HQC everywhere, as there are no longer non-RMRS versions of HQC.

I made a number of small changes to the reference code, mostly to eliminate undefined or implementation-defined behaviour. The only substantial change is the addition of a Barrett reduction routine in the code for constant-weight vector sampling. This was to address #482. Please pay special attention to this code when reviewing; it's found in vector.c.

The latest submission of HQC generates KATs using a custom PRNG instead of the one provided by NIST. I added an implementation of this PRNG in the test directory and modified the test files so that it would be used in the NIST KAT tests.

It might be easier to review against the reference code: my fork of the package-pqclean repo can help with this.

Fixes #482.

Manually checked properties

• Generated Github workflow (run .github/workflows/generate_workflows.py) (new schemes)
• No stringification macros
• Output-parameter pointers in functions are on the left
• Negative return values on failure of API functions (within restrictions of FO transform).
• variable declarations at the beginning (except in for (size_t i=...)
• Optional:
  • All integer types are of fixed size, using stdint.h types (including uint8_t instead of unsigned char)
  • Integers used for indexing are of size size_t