Investigate how to run Bridges Zombienet tests (Polkadot SDK at least, Polkadot Fellows) within PRs as part of this CI

[bkontur]

When upgrading or updating the relayer's code here (e.g., new runtime version, Polkadot SDK bump, etc.), we need to manually test the new substrate-relay binary with different bridges. While we can do this locally, I’m sure we can also integrate it into the CI as part of PRs.