Add txpool function to find the next free nonce

[mattsse]

Describe the feature

we need a function that given an on chain nonce it should return the next missing nonce by an address

this is similar to

reth/crates/transaction-pool/src/traits.rs

Lines 353 to 357 in 0b63972

	/// Returns the highest transaction sent by a given user
	fn get_highest_transaction_by_sender(
	&self,
	sender: Address,
	) -> Option<Arc<ValidPoolTransaction<Self::Transaction>>>;

but should also accept a nonce and return the highest transaction without a nonce gap

Additional context

No response

[kien6034]

i would like to work on this

[onbjerg]

Thanks! I've assigned you to the issue. If you feel stuck, open up a draft PR with your questions and someone will help you. If you are prevented from solving the issue, let me know and I will unassign you 😄

[kien6034]

thank you