feat(l1): match the amount of peers to target

[ElFantasma]

Motivation
Currently we don't limit the amount of connected peers, but we have an internal constant for that

Description
Avoid new connections if the amount of connected peers matches the target

Closes #4862

[github-actions]

Lines of code report

Total lines added: 29
Total lines removed: 16
Total lines changed: 45

Detailed view

+--------------------------------------------------------+-------+------+
| File                                                   | Lines | Diff |
+--------------------------------------------------------+-------+------+
| ethrex/cmd/ethrex/cli.rs                               | 536   | +12  |
+--------------------------------------------------------+-------+------+
| ethrex/crates/networking/p2p/discv4/peer_table.rs      | 907   | -8   |
+--------------------------------------------------------+-------+------+
| ethrex/crates/networking/p2p/discv4/server.rs          | 480   | -7   |
+--------------------------------------------------------+-------+------+
| ethrex/crates/networking/p2p/metrics.rs                | 588   | +6   |
+--------------------------------------------------------+-------+------+
| ethrex/crates/networking/p2p/peer_handler.rs           | 1750  | -1   |
+--------------------------------------------------------+-------+------+
| ethrex/crates/networking/p2p/rlpx/connection/server.rs | 975   | +5   |
+--------------------------------------------------------+-------+------+
| ethrex/crates/networking/p2p/rlpx/error.rs             | 117   | +2   |
+--------------------------------------------------------+-------+------+
| ethrex/crates/networking/p2p/rlpx/initiator.rs         | 101   | +4   |
+--------------------------------------------------------+-------+------+