support more possible inputs for relay key config

[ZanCorDX]

the relay secret key configuration option was not compatible with BIP44 input, e.g. the output of a mnemonic seed phrase and a given path in the tree

this PR now supports this feature which was simplest by just exposing a BIP44 compatible API the underlying ethereum-consensus dependency

✅ I have completed the following steps:

• Run make lint
• Run make test
• Added tests (if applicable)

[Copilot]

Pull Request Overview

This PR adds support for BIP44-compatible inputs for relay secret key configuration by updating the key parsing logic to accept various input formats including mnemonic seed phrase outputs.

• Updated the secret key parsing logic to use hex decoding and bytes-based key creation
• Added hex module import to support the new decoding functionality

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[Copilot]

The change from SecretKey::try_from(resolved_key)? to hex decoding breaks backward compatibility with existing non-hex secret key formats. The original code likely supported multiple input formats, but this change forces all inputs to be hex-encoded. Consider adding format detection or maintaining support for the original format alongside hex decoding.

Suggested change

	let input = hex::decode(resolved_key)?;
	SecretKey::from_bytes(&input)?
	// Try legacy format first, then fallback to hex decoding
	match SecretKey::try_from(resolved_key.clone()) {
	Ok(key) => key,
	Err(_) => {
	let input = hex::decode(resolved_key)?;
	SecretKey::from_bytes(&input)?
	}
	}