Superblock metering

[cdetrio]

[WIP dont merge]

When executing metered wasm (where the gas cost table is 1 for every instruction), the gas used should be equal to the number of wasm instructions executed. This achieves that for bn128_mul, except for an off-by-one error.

## ecmul_minified_unmetered.wasm
total instructions executed: 8039712

## ecmul_minified_metered.wasm
total instructions executed: 8217634
total useGas calls: 88961
total gas used: 8039713

8039713 - 8039712 = 1