feat(anvil): Anvil --unlocked for auto-impersonation on instance creation

[Sabnock01]

Motivation

It should be possible to auto-impersonate accounts upon the initial spawning of Anvil instances.

Solution

This PR introduces an --auto-impersonate flag which enables auto impersonation of accounts when the anvil instance is created. This helps avoid the need to use curl or cast rpc to set anvil_autoImpersonateAccount to true when the Anvil instance is spawned. Resolves #5334

[mattsse]

--unlocked already has a slightly different meaning in cast,
perhaps we rename this to --auto-impersonate instead?

[Sabnock01]

Question, would the call to the EthApi::anvil_auto_impersonate_account method be done in spawn or somewhere else?

[mattsse]

we can either call the rpc handler after creating the EthApi type:

foundry/anvil/src/lib.rs

Lines 148 to 159 in c78a811

	// create the cloneable api wrapper
	let api = EthApi::new(
	Arc::clone(&pool),
	Arc::clone(&backend),
	Arc::new(signers),
	fee_history_cache,
	fee_history_service.fee_history_limit(),
	miner.clone(),
	logger,
	filters.clone(),
	transaction_order,
	);

foundry/anvil/src/eth/api.rs

Lines 1382 to 1389 in c78a811

	/// If set to true will make every account impersonated
	///
	/// Handler for ETH RPC call: `anvil_autoImpersonateAccount`
	pub async fn anvil_auto_impersonate_account(&self, enabled: bool) -> Result<()> {
	node_info!("anvil_autoImpersonateAccount");
	self.backend.auto_impersonate_account(enabled).await?;
	Ok(())
	}

or directly on the backend

foundry/anvil/src/eth/backend/mem/mod.rs

Lines 318 to 322 in c78a811

	/// If set to true will make every account impersonated
	pub async fn auto_impersonate_account(&self, enabled: bool) -> DatabaseResult<()> {
	self.cheats.set_auto_impersonate_account(enabled);
	Ok(())
	}

these are actually infallible and I think we should remove the result, at least for the backend function

so lets do:

1. remove result return type from backend::auto_impersonate_account
2. call backend::auto_impersonate_account(true) if config.auto_impersonate

[Sabnock01]

Thanks! This was very helpful. I've tested this locally through cast send commands and it works. Let me know if there's anything else I should add!

[mattsse]

lgtm, one nit