Move txpool sequencer out of tracked pool

[andr-dev]

The txpool sequencer was placed in the tracked subdirectory and directly called by the tracked map since we can only sequence tracked txs (those with nonce guaranteed to be greater than or equal to the last committed account nonce). The decision to have it be called by the tracked map however is an implementation detail.

Since we are moving more towards a world where the pool maps are "simple" datastructures, this PR moves the sequencer out of the tracked subdirectory and performs the tx sequencing directly in EthTxPool.

[Copilot]

Pull Request Overview

This PR refactors the transaction sequencing logic by moving ProposalSequencer from the tracked subdirectory to the main pool module, making it a first-class component directly managed by EthTxPool.

Key Changes:

• Moved sequencer from tracked/sequencer.rs to pool/sequencer.rs
• Extracted create_proposal method from TrackedTxMap into new sequence_user_transactions method in EthTxPool
• Modified ProposalSequencer::new to accept an iterator instead of direct IndexMap reference

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
monad-eth-txpool/src/pool/tracked/mod.rs	Removed sequencer module and create_proposal method; added iter() method to expose tracked transactions
monad-eth-txpool/src/pool/sequencer.rs	Updated imports and changed ProposalSequencer::new to accept iterator parameter; removed unused chain_id parameter from build_proposal
monad-eth-txpool/src/pool/mod.rs	Added sequencer module; implemented new sequence_user_transactions method; refactored create_proposal to use new sequencing approach

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