feat: Snap/Torrent-style initial sync

[rymnc]

Currently, syncing a node from scratch can be done only via p2p. We lack the ability to share backups of the databases between filesystems/os abstractions and hence heavily rely on p2p for syncing when rather someone's database could initially be bootstrapped by another mechanism.

Sub-Issues

• Platform agnostic backups/recovery for rocksdb.
  • feat(rocksdb): remove getters for internal rocksdb handles, expose backup instead #2535
• Describe chunking of backup with compression. We can do some interesting things by having magnet links for block ranges, but mvp can have just one magnet link.
• Describe SnapSync RunnableService conditionally mounted based on cli args.

Definition of Done

• I can start a fuel node which generates a backup every x days and serves it over the torrent protocol
• I can start a fuel node with --snap-sync --snap-sync-magnet-uri <> to initially bootstrap my fuel node