Support ownership transfer and acceptance for Ownable2Step contracts

[nkuba]

Initially proposed by @r-czajkowski in thesis/acre#91 (comment).

We should consider supporting Ownable2Step way of transferring ownership on local deployment, to cover the execution of acceptOwnership function in our helpers.

Example of a deployment script that we could try to cover with helpers:

  await deployments.execute(
    "AcreBitcoinDepositor",
    { from: deployer, log: true, waitConfirmations: 1 },
    "transferOwnership",
    governance,
  )

  if (hre.network.name !== "mainnet") {
    await deployments.execute(
      "AcreBitcoinDepositor",
      { from: governance, log: true, waitConfirmations: 1 },
      "acceptOwnership",
    )
  }