Extract BLS lib files to separate repo/package

[jacque006]

Problem

The Solidity BLS libs in this repo are a separate and reusable component outside of the optimistic rollup functionality in the contracts. As more projects use or build upon BLS functionality they will likely want these components. Currently they must correctly copy/pasta the correct pieces out, and will not have an easy way to get updates.

https://github.com/jzaki/bls-wallet-contracts is one current example.

We already have extracted similar functionality from JS/TS to https://github.com/thehubbleproject/hubble-bls

Solution

• Create the Github repo thehubbleproject/hubble-bls-contracts.
• Extract BLS Solidity libraries from https://github.com/thehubbleproject/hubble-contracts/tree/master/contracts/libs (BLS.sol, BNPairingPrecompileCostEstimator.sol, ModExp.sol, etc.) to an new repo that will be an npm package (like https://github.com/OpenZeppelin/openzeppelin-contracts)
• Do the same for tests that verify the functionality in those files, such as test/fast/bls.test.ts.
• Setup Github actions pipeline to run tests and deploy the package to @thehubbleproject/bls-contracts on releases. We can likely copy/pasta parts of https://github.com/thehubbleproject/hubble-bls
• (Optional) If possible, extract the deployment scripts and pipeline for BNPairingPrecompileCostEstimator.sol to make it easier for projects to deploy needed BLS deps.

[jacque006]

FYI @ChihChengLiang @kautukkundan @jzaki