Shrink persisted fork choice data (#7805)

Closes:

- https://github.com/sigp/lighthouse/issues/7760


  - [x] Remove `balances_cache` from `PersistedForkChoiceStore` (~65 MB saving on mainnet)
- [x] Remove `justified_balances` from `PersistedForkChoiceStore` (~16 MB saving on mainnet)
- [x] Remove `balances` from `ProtoArray`/`SszContainer`.
- [x] Implement zstd compression for votes
- [x] Fix bug in justified state usage
- [x] Bump schema version to V28 and implement migration.

beacon_node/beacon_chain/Cargo.toml

@@ -1,4 +1,4 @@
- 
+
 [package]
 name = "beacon_chain"
 version = "0.2.0"
@@ -65,6 +65,7 @@ tracing = { workspace = true }
 tree_hash = { workspace = true }
 tree_hash_derive = { workspace = true }
 types = { workspace = true }
+zstd = { workspace = true }
 
 [dev-dependencies]
 criterion = { workspace = true }