refactor(l1): modularize sync code & add doc comments for each module

[fmoletta]

Motivation
The code for sync has grown significantly since its start, and having it all under the same module can make it very hard to follow.
This PR aims to solve this by separating each different job into different modules and adding module-level documentation for each, explaining how each part of the sync works and integrates to the system as a whole

Description

• Separate sync code into different modules, one for each separate functionality
• Add doc comments for each individual module explaining its purpose and mechanics

Notes for merging:
This PR will likely conflict with #1936 but it has the same exact code, only moving it across modules, so it should be safe to solve all conflicts by keeping the changes from this PR alone. Alternatively, you can also merge this PR into #1936 as it has no conflicts and then merge #1936

[github-actions]

| File                                                                           | Lines | Diff |
+--------------------------------------------------------------------------------+-------+------+
| /home/runner/work/ethrex/ethrex/crates/networking/p2p/sync.rs                  | 403   | -791 |
+--------------------------------------------------------------------------------+-------+------+
| /home/runner/work/ethrex/ethrex/crates/networking/p2p/sync/bytecode_fetcher.rs | 43    | +43  |
+--------------------------------------------------------------------------------+-------+------+
| /home/runner/work/ethrex/ethrex/crates/networking/p2p/sync/state_healing.rs    | 118   | +118 |
+--------------------------------------------------------------------------------+-------+------+
| /home/runner/work/ethrex/ethrex/crates/networking/p2p/sync/state_sync.rs       | 234   | +234 |
+--------------------------------------------------------------------------------+-------+------+
| /home/runner/work/ethrex/ethrex/crates/networking/p2p/sync/storage_fetcher.rs  | 150   | +150 |
+--------------------------------------------------------------------------------+-------+------+
| /home/runner/work/ethrex/ethrex/crates/networking/p2p/sync/storage_healing.rs  | 97    | +97  |
+--------------------------------------------------------------------------------+-------+------+
| /home/runner/work/ethrex/ethrex/crates/networking/p2p/sync/trie_rebuild.rs     | 236   | +236 |
+--------------------------------------------------------------------------------+-------+------+

Total lines added: +878
Total lines removed: 791
Total lines changed: 1669