Refactor upgradability tests

[heueristik]

Description

Refactored upgrade tests to use hardhat-upgrades properly. It now alerts if the storage layout becomes corrupted.

To try it out, make a change to a contract and execute yarn clean && yarn build && yarn test to see the effects.

Task ID: OS-408

Type of change

• Bug fix (non-breaking change which fixes an issue)

Checklist:

• I have selected the correct base branch.
• I have performed a self-review of my own code.
• I have commented my code, particularly in hard-to-understand areas.
• I have made corresponding changes to the documentation.
• My changes generate no new warnings.
• Any dependent changes have been merged and published in downstream modules.
• I ran all tests with success and extended them if necessary.
• I have updated the CHANGELOG.md file in the root folder.
• I have updated the DEPLOYMENT_CHECKLIST file in the root folder.
• I have updated the UPDATE_CHECKLIST file in the root folder.

[mathewmeconry]

LGTM
Can you confirm that the test coverage doesn't decrease and that we also cover the same unhappy paths as before?

[heueristik]

LGTM Can you confirm that the test coverage doesn't decrease and that we also cover the same unhappy paths as before?

Yes @mathewmeconry, the previous tests weren't actually doing anything useful: hardhat-upgrades wasn't used and the automated tests were upgrading every contract to ethers.constants.AddressZero and used the PluginUUPSUpgradeableV1Mock__factory, which doesn't make any sense.