Add a test with proxy creation

[Tbaut]

As per https://github.com/ChainSafe/Multix/pull/466#pullrequestreview-1806687715

Ideally, we should now add not only the creation of the multisig, but also the pure, and verify that the UI updates showing the pure in the header once it's available. [...] I think it could be added by just extending the test with the pure creation.