Use the ledger hash to draw selections

[Eitu33]

Introduction

This is the second issue for the implementation of https://github.com/massalabs/massa/discussions/2968

TODO

• [ ] Save a snapshot of the ledger hash in PoS at every end of cycle
• [ ] Concat the C-2 seed with the C-3 ledger hash
• [ ] Use this as new seed when drawing selections

Related issues

https://github.com/massalabs/massa/issues/2986

[damip]

Ideally, we should use the hash of the whole state (not only the ledger)

[AurelienFT]

Closed in #2986