chore: add E2E test suite to run on a weekly basis for testing deployment and verification across various block explorers

We currently require a lot of manual smoke testing to make sure we don't introduce regressions when we make modifications to the verification process.

The proposal by @grandizzy is to have a workflow / test suite that on a weekly basis would perform automated tests to make sure the verification flow works as intended.

This should include multiple blockchains and multiple explorers.

It can run in the CI with a dedicated private key / keystore we just use for this purpose.