Add benchmark on BLS by building on top of BN256 with lattice decomposition

[autholykos]

While the lattices branch of bn256 is not expected to provide a substantial speed-up in signature verification (since it uses pairing operation, unaffected by the lattice-decomposition), it is equally true that signature generation and aggregation might benefit substantially from a more efficient scalar multiplication.

This task is to benchmarks against master and lattices branches

[autholykos]

Benchmarks confirm the expected performance improvement on signature generation using dusk-network/bn256@lattices compared to dusk-network/bn256@master.

*Specs

system         ZenBook S UX391UA
bus               UX391UA
memory       64KiB BIOS
memory       16GiB System Memory LPDDR3 
processor    Intel(R) Core(TM) i7-8550U CPU @ 1.80GHz
bridge          Xeon E3-1200 v6/7th Gen Core Processor Host Bridge/DRAM Registers

• Master

  BenchmarkSign-8                                             3000            391747 ns/op
  BenchmarkAggregate10Signatures-8                          300000              4370 ns/op
  BenchmarkAggregate100Signatures-8                          30000             47491 ns/op
  BenchmarkAggregate1000Signatures-8                          3000            492140 ns/op
  BenchmarkVerifySingleSignature-8                             500           3603258 ns/op
  BenchmarkVerifyUnsafeSingleSignature-8                       500           3128698 ns/op
  BenchmarkVerifySingleCompressedSignature-8                   500           3199448 ns/op
  BenchmarkVerifySingleCompressedUnsafeSignature-8             500           3000716 ns/op

• Lattices

  BenchmarkSign-8                                             5000            254454 ns/op
  BenchmarkAggregate10Signatures-8                          300000              4337 ns/op
  BenchmarkAggregate100Signatures-8                          30000             47310 ns/op
  BenchmarkAggregate1000Signatures-8                          3000            496335 ns/op
  BenchmarkVerifySingleSignature-8                             500           3398603 ns/op
  BenchmarkVerifyUnsafeSingleSignature-8                       500           3073851 ns/op
  BenchmarkVerifySingleCompressedSignature-8                   500           3124125 ns/op
  BenchmarkVerifySingleCompressedUnsafeSignature-8             500           3134376 ns/op