Add config setting for pending block behaviour

[mattsse]

Describe the feature

currently we're building an entire block in rpc, this isn't always desired:

reth/crates/rpc/rpc-eth-api/src/helpers/pending_block.rs

Lines 246 to 252 in 5bc8589

	let mut best_txs =
	self.pool().best_transactions_with_attributes(BestTransactionsAttributes::new(
	block_env.basefee,
	block_env.blob_gasprice().map(|gasprice| gasprice as u64),
	));
	while let Some(pool_tx) = best_txs.next() {

ideally this behaviour is configureable via rpcargs and ethconfig

reth/crates/node/core/src/args/rpc_server.rs

Line 44 in 5bc8589

pub struct RpcServerArgs {

reth/crates/rpc/rpc-eth-types/src/builder/config.rs

Line 20 in 5bc8589

pub struct EthConfig {

for this we can include a setting lik

pending_block: empty|none|full

for this we need another enum for these states, this behaviour we then need to respect when handling the block

Additional context

No response

[iTranscend]

can i?

[mattsse]

cool, assigned @iTranscend