Update some shard u16 to u64

This is pretty hacky, is just serving my purpose for `BeaconChain`.
These structs will need to be fully updated to the latest spec.

beacon_chain/types/src/validator_record.rs

@@ -14,7 +14,7 @@ pub enum ValidatorStatus {
 #[derive(Debug, Clone, PartialEq)]
 pub struct ValidatorRecord {
     pub pubkey: PublicKey,
-    pub withdrawal_shard: u16,
+    pub withdrawal_shard: u64,
     pub withdrawal_address: Address,
     pub randao_commitment: Hash256,
     pub randao_last_change: u64,

beacon_chain/types/src/validator_registration.rs

@@ -5,7 +5,7 @@ use bls::{create_proof_of_possession, Keypair, PublicKey, Signature};
 #[derive(Debug, Clone, PartialEq)]
 pub struct ValidatorRegistration {
     pub pubkey: PublicKey,
-    pub withdrawal_shard: u16,
+    pub withdrawal_shard: u64,
     pub withdrawal_address: Address,
     pub randao_commitment: Hash256,
     pub proof_of_possession: Signature,

beacon_chain/validator_induction/src/inductor.rs

@@ -7,7 +7,7 @@ pub const DEPOSIT_GWEI: u64 = 32_000_000_000;
 /// Inducts validators into a `CrystallizedState`.
 pub struct ValidatorInductor {
     pub current_slot: u64,
-    pub shard_count: u16,
+    pub shard_count: u64,
     validators: Vec<ValidatorRecord>,
     empty_validator_start: usize,
 }