[TASK] Add Tests for Substrate governor updates flow

[shekohex]

Overview

Add governor update test case for substrate based chains. Relayer should watch for PublicKeySignatureChanged and relay set_maintainer transaction to substrate chain.

// msg = nonce+dkg_key
 let mut message = nonce.to_be_bytes().to_vec();
 message.extend_from_slice(&new_maintainer);

 let set_maintainer_call = SetMaintainer {
            message: BoundedVec(message.clone()),
            signature: BoundedVec(signature.clone()),
 };

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Checklist

• [ ] Update relayer code to construct msg = nonce+dkg_key
• [ ] Write governor update test

[salman01zp]

closed by #371