Feature: override readArtifact during getContractFactory()

[heri16]

Certain plugins like hardhat-deploy-ethers would benefit from being able to override readArtifact during getContractFactory() from packages/hardhat-ethers/src/internal/helpers.ts.

hardhat-deploy-ethers currently does not extend from @nomiclabs/hardhat-ethers, even though it is mostly the same.

[heri16]

After analyzing third party plugin called hardhat-deploy-ethers, it looks like the features added to @nomiclabs/hardhat-ethers are getNamedSigners, getUnnamedSigners, and these line changes below:

https://github.com/wighawag/hardhat-deploy-ethers/blob/main/src/helpers.ts#L237

https://github.com/wighawag/hardhat-deploy-ethers/blob/a6053c7ceb39bc17064b356b628dc381b9aacb9d/src/helpers.ts#L237

async function _getArtifact(
  hre: HardhatRuntimeEnvironment,
  name: string
): Promise<Artifact> {
  const deployments = (hre as any).deployments;
  if (deployments !== undefined) {
    return deployments.getArtifact(name);
  }
  return hre.artifacts.readArtifact(name);
}

async function getContractFactoryByName<T extends ethers.ContractFactory>(
  hre: HardhatRuntimeEnvironment,
  contractName: string,
  signerOrOptions?: ethers.Signer | string | FactoryOptions
): Promise<T> {
  const artifact = await _getArtifact(hre, contractName);
  ...
}

This is a good first step to enable the reuse of @nomiclabs/hardhat-ethers, in such a third-party plugin.

[fvictorio]

Closing this in favor of #1040.