[Early Draft] feat(l1): download all headers from new to old as first step of full sync

[fmoletta]

Motivation
In order to properly handle reorgs, we should download headers from the latest announced fcu head until me meet our local chain instead of requesting headers from our current head till we reach the fcu head, as our current head may not be part of the canonical chain after a reorg.
The main behaviour changes imposed by this are that
A) We must request all headers before we can begin to execute the blocks
B) We are no longer able to keep all headers in memory (in case of long syncs)

Description

Closes #issue_number

[github-actions]

Lines of code report

Total lines added: 113
Total lines removed: 0
Total lines changed: 113

Detailed view

+---------------------------------------------+-------+------+
| File                                        | Lines | Diff |
+---------------------------------------------+-------+------+
| ethrex/crates/networking/p2p/sync.rs        | 1285  | +61  |
+---------------------------------------------+-------+------+
| ethrex/crates/storage/api.rs                | 231   | +6   |
+---------------------------------------------+-------+------+
| ethrex/crates/storage/store.rs              | 1440  | +10  |
+---------------------------------------------+-------+------+
| ethrex/crates/storage/store_db/in_memory.rs | 540   | +10  |
+---------------------------------------------+-------+------+
| ethrex/crates/storage/store_db/rocksdb.rs   | 1136  | +26  |
+---------------------------------------------+-------+------+