Find a rust replacement for BlsVerify

[gjermundgaraba]

Currently, we rely fast_aggregate and aggregate of BLS signatures being provided by a CosmWasm CustomQuery from the chain itself (i.e. the code is in go and being called from the CosmWasm contract).

The reason for this is because there are currently no production ready rust libraries for this (it seems). If something exists that we can use (we will not write this ourselves), we should use that instead.

We currently use https://github.com/Snowfork/milagro_bls for tests, but that repo has some severe warnings on not being production ready, so that is not an option for the moment.