run FEC decoding test in a loop
changelog
- refactor k and n into variables
- run the decoding FEC test in a loop from (k - 1) \rho + 1 to k \rho, where \rho is the curve number of bytes per scalar field element, e.g. 31 for BLS-12-381
- add a NOTE about having too few bytes and elements, i.e. below (k - 1) \rho + 1
- add a FIXME about having too many bytes and elements, i.e. above k \rho