Migrating ownership on L2 via Gnosis Multisig

[i-stam]

Summary

The owner.js script that is used for migrating ownership to a multisig after a system upgrade is taylor made for Gnosis Safe. We want to modify or develop a new one for supporting the use of Gnosi Multisig which is the only multisg wallet supported initially on Optimism.

Relevant Info

Check #1154 for background on Gnosis Multisig
Multisig repo: https://github.com/ScopeLift/ovm-og-multisigwallet
There are 2 options to approach the problem:

1. Modify the current script (owner.js) to be flexible enough to handle all cases i.e. migration to EOA/Multisig, evm/ovm, Safe/Multisig.
2. Create 3 distinct scripts: 1) migrate to Gnosis Safe 2) migrate to an EOA 3)migrate to Gnosis Multisig.

Dev Tasks

• Develop a new script or modify the existing one for migrating all the ownership of a test instance to the multisig and doing a system upgrade.
  PR: Use Gnosis Multisig for managing contract ownership on L2 #1188
• Test the owner migration in Kovan-ovm (test + official).
• Test the official owner migration (mainnet-ovm).