feat(l1): pull new peers from discovery

[MegaRedHand]

Motivation

We aren't actively finding new nodes.

Description

This PR adds a new RLPxServer that actively initiates new connections and keeps a healthy eth-enabled peerbase. The idea is to have something like:

• The RLPxServer starts N workers that perform recursive lookups through discv4 (we need workers for this to not block the server).
• P2P consumers (like the Syncer) call the server to get open peer connections.

[github-actions]

Lines of code report

Total lines added: 317
Total lines removed: 35
Total lines changed: 352

Detailed view

+-----------------------------------------------+-------+------+
| File                                          | Lines | Diff |
+-----------------------------------------------+-------+------+
| ethrex/crates/networking/p2p/discv4/lookup.rs | 385   | +68  |
+-----------------------------------------------+-------+------+
| ethrex/crates/networking/p2p/discv4/server.rs | 819   | -26  |
+-----------------------------------------------+-------+------+
| ethrex/crates/networking/p2p/network.rs       | 160   | +7   |
+-----------------------------------------------+-------+------+
| ethrex/crates/networking/p2p/rlpx.rs          | 9     | +2   |
+-----------------------------------------------+-------+------+
| ethrex/crates/networking/p2p/rlpx/lookup.rs   | 79    | +79  |
+-----------------------------------------------+-------+------+
| ethrex/crates/networking/p2p/rlpx/p2p.rs      | 304   | +36  |
+-----------------------------------------------+-------+------+
| ethrex/crates/networking/p2p/rlpx/server.rs   | 125   | +125 |
+-----------------------------------------------+-------+------+
| ethrex/crates/networking/rpc/admin/peers.rs   | 103   | -9   |
+-----------------------------------------------+-------+------+