refactor(l1): parallelize request_block_headers function

[ricomateo]

Motivation
The request_block_headers function is quite slow due to its sequential approach, since it queries block headers from one peer at a time, waiting for a response from one peer (it currently waits up to 15 seconds) before trying the next.
This makes the process very slow since some peers may return invalid data, or they may even not respond.

Description
This PR modifies the request_block_headers function to request the block headers to multiple peers in parallel instead of querying them sequentially. With this approach the node no longer waits for one peer to respond before querying the next one. Instead, all the peers are queried simultaneously, and the first valid response is returned, significantly speeding up the process.

Closes: None

[github-actions]

Lines of code report

Total lines added: 264
Total lines removed: 40
Total lines changed: 304

Detailed view

+-------------------------------------------------+-------+------+
| File                                            | Lines | Diff |
+-------------------------------------------------+-------+------+
| ethrex/cmd/ethrex/cli.rs                        | 455   | -4   |
+-------------------------------------------------+-------+------+
| ethrex/crates/l2/contracts/bin/deployer/main.rs | 624   | +3   |
+-------------------------------------------------+-------+------+
| ethrex/crates/l2/monitor/app.rs                 | 304   | -8   |
+-------------------------------------------------+-------+------+
| ethrex/crates/l2/sdk/src/sdk.rs                 | 737   | +256 |
+-------------------------------------------------+-------+------+
| ethrex/crates/networking/p2p/kademlia.rs        | 625   | +5   |
+-------------------------------------------------+-------+------+
| ethrex/crates/networking/p2p/peer_handler.rs    | 718   | -25  |
+-------------------------------------------------+-------+------+
| ethrex/crates/vm/levm/src/db/gen_db.rs          | 244   | -3   |
+-------------------------------------------------+-------+------+

[mpaulucci]

What happens if:

• One peer is very slow and times out. All blocks will be discarded?
• Same question but if a peer returns invalid blocks or blocks from another chain?