Bundle Multiple EVM Providers

[salman01zp]

Summary of changes

• Updated http-endoint config for EVM chains to support both single and Multpli RPC endpoint input

/// configuration for adding http endpoints.
#[derive(Debug, Clone, Deserialize, Serialize)]
#[serde(untagged)]
pub enum HttpEndpoint {
    /// Single http endpoint
    Single(RpcUrl),
    /// Multiple http endpoints
    Multiple(Vec<RpcUrl>),
}

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• Implement MultiProvider Client which takes multiple Evm provider as input and processes request in a round-robin method.

/// MultiProvider is a JsonRpcClient that will round-robin requests to the underlying providers.
#[derive(Debug, Clone)]
pub struct MultiProvider<P> {
    providers: Arc<Vec<P>>,
    last_used: Arc<AtomicUsize>,
}

impl<P> MultiProvider<P> {
    pub fn new(providers: Arc<Vec<P>>) -> Self {
        Self {
            providers,
            last_used: Default::default(),
        }
    }
}

MultiProvider implements JsonRpcClient which is then consumed by RetryClient

let multi_provider = MultiProvider::new(Arc::new(providers));
// Wrap the provider with a retry client.
let retry_client = RetryClientBuilder::default()
    .timeout_retries(u32::MAX)
    .rate_limit_retries(u32::MAX)
    .build(multi_provider, WebbHttpRetryPolicy::boxed());

Reference issue to close (if applicable)

• Closes #499

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Code Checklist

• [ ] Tested
• [ ] Documented