Add HQC from PQClean take 2

[dstebila]

Adds HQC from PQClean. HQC makes use of nistseedexpander so this adds that as well.

Depends on #803

Replaces #804.

Fixes #709.

• [No] 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.)
• [Yes] Does this PR change the the list of algorithms available -- either adding or removing? (If so, PRs in OQS-OpenSSL, OQS-BoringSSL, and OQS-OpenSSH will also be required by the time this is merged.)

Note that HQC-256 variants use lots of stack space (similar to Classic McEliece). Downstream consumers will have to be updated to take this into account.