Update bn254 cost

[jhb10c]

This adjusts the gas weights for bn254 operations. The makes the ec operations at parity for 1 billion gas being executed at 1 second.

This would complete: https://github.com/category-labs/category-internal/issues/836

[jhb10c]

One final note (im delete this comment btw):

1. The other precompiles should be benchmarked. Highly likely they will also be mispriced. This will be done after benchmarking framework is more developed.
2. Longterm solution would be to implement something philosophically similar to EIP6601.