Proto: benchmark + gas costs for tz4 accounts, signatures

The following discussion from !5444 (merged) should be addressed:

• @mebsout started a discussion: (+1 comment)

  Opening a thread to not forget to have an issue for the gas benchmarks for BLS signature checks. (Or maybe we already have this benchmark @igarnier @lrand?).

Benchmark included, the gas needs to be generated. Note: this changes the workload encoding. Also the generators have been modified, they need to be run again to get updated michelson data.

On my machine I have a constant of 1.2M