Chainweb Post-Quantum WIP

[kdafriend]

• Use the pact Post-Quantum branch and fix tests
• Guard Pact5 for SLH Signatures
• Enable SLH signatures by fork numbers.

A new type called PactPPKScheme has been created to unify Pact4 and Pact5 signature schemes. The mechanism used by Pact4 functions to allow or disallow schemes between forks. has been ported to Pact5 functions. In both cases, we use PactPPKScheme and validPPKSchemes to guard the schemes.

Some test/benchmarks appeared to be broken (and fixed) because of some mix between Pact4/Pact5 parsers / execution.

TODO:

• Tests
• Gas harge signatures length, and processing (a SLH signature verification is an heavy operation)