Relax the ConfigureEvm trait to allow custom block executors

[debjit-bw]

Describe the feature

The return types of fn executor and fn batch_executor hardcode -> BasicBlockExecutor<&Self, DB>. This prevents custom block executors from being used.

reth/crates/evm/evm/src/lib.rs

Lines 282 to 292 in 3338c5a

	/// Returns a new [`BasicBlockExecutor`].
	#[auto_impl(keep_default_for(&, Arc))]
	fn executor<DB: Database>(&self, db: DB) -> BasicBlockExecutor<&Self, DB> {
	BasicBlockExecutor::new(self, db)
	}
	/// Returns a new [`BasicBlockExecutor`].
	#[auto_impl(keep_default_for(&, Arc))]
	fn batch_executor<DB: Database>(&self, db: DB) -> BasicBlockExecutor<&Self, DB> {
	BasicBlockExecutor::new(self, db)
	}

If we need deeper customisations (for example, changing the fn execute_one or fn execute_one_with_state_hook, we need to have a CustomBlockExecutor, which cannot be returned from fn executor, which is used for the block execution.

Instead, fn executor and fn batch_executor should return an impl type instead of the concrete BasicBlockExecutor.

Additional context

For context, I want to modify the block's execution so that before execution I can use the inspector and an evm in order to simulate transactions and flag certain transactions which calls sstores on specific contracts. Restricting the inspector in impl<'db, DB, E, Spec, R> BlockExecutor doesn't work because the higher level function create_evm, which is called from evm_for_block expects a NoOpInspector, and a couple of other issues.

Configuring the fn execute_one was possible prior to v1.4.3 due to the BlockExecutorFactory, but since that has been removed, we need a different way of customizing it. With this hardcoded return type in ConfigureEvm, reth becomes less configurable.

[nadtech-hub]

I'd like to take on it

[debjit-bw]

cc: @mattsse