refactor(l1): enhance mempool oldest removal

[gianbelinche]

Motivation
The removal of elements from the mempool when it is full is not efficient.

Description
Now the array that represent the order of insertion to the mempool is a vecdeque, which is not changed when an arbitrary element is removed from the mempool.
Only when the mempool is full, we remove from the vecdeque until we find an element present in the mempool.
Also if the vecdeque is greater than 150% of the maximum mempool size, we prune it, keeping only the txs that are actually in the mempool, preserving the order.

Closes #4605

[Copilot]

Pull Request Overview

This PR refactors the mempool to improve efficiency of oldest transaction removal when the pool is full. The main changes involve restructuring the mempool's internal data structures and optimizing the removal process.

• Consolidates all mempool data structures into a single MempoolInner struct protected by one RwLock
• Replaces the Vec<H256> order tracking with a VecDeque<H256> that is lazily cleaned
• Implements a pruning mechanism that removes stale entries from the order queue when it exceeds 150% of max capacity

Reviewed Changes

Copilot reviewed 1 out of 1 changed files in this pull request and generated 2 comments.

File	Description
crates/blockchain/mempool.rs	Major refactoring of mempool structure and oldest transaction removal logic
crates/networking/p2p/tx_broadcaster.rs	Updates method call to handle new return type

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[github-actions]

Lines of code report

Total lines added: 13
Total lines removed: 0
Total lines changed: 13

Detailed view

+-------------------------------------+-------+------+
| File                                | Lines | Diff |
+-------------------------------------+-------+------+
| ethrex/crates/blockchain/mempool.rs | 727   | +13  |
+-------------------------------------+-------+------+