Shuffling for 32 bit platforms (#7725)

- In shuffling, a the raw_pivot (u64) is cast to a usize which will break on 32 bit systems. Now it is modulo'ed with the list_size first then cast to a usize.
- ruint doesn't implement shifting with u64's on 32-bit arch. Since `prefix_bits` is u8 and NODE_ID_BITS = 256, we use them as u32's instead.

See: https://docs.rs/ruint/latest/src/ruint/bits.rs.html#711

consensus/swap_or_not_shuffle/src/shuffle_list.rs

@@ -96,8 +96,7 @@ pub fn shuffle_list(
     loop {
         buf.set_round(r);
 
-        let pivot = buf.raw_pivot() as usize % list_size;
-
+        let pivot = (buf.raw_pivot() % list_size as u64) as usize;
         let mirror = (pivot + 1) >> 1;
 
         buf.mix_in_position(pivot >> 8);

consensus/types/src/subnet_id.rs

@@ -11,7 +11,7 @@ const MAX_SUBNET_ID: usize = 64;
 
 /// The number of bits in a Discovery `NodeId`. This is used for binary operations on the node-id
 /// data.
-const NODE_ID_BITS: u64 = 256;
+const NODE_ID_BITS: u32 = 256;
 
 static SUBNET_ID_TO_STRING: LazyLock<Vec<String>> = LazyLock::new(|| {
     let mut v = Vec::with_capacity(MAX_SUBNET_ID);
@@ -102,7 +102,7 @@ impl SubnetId {
         spec: &ChainSpec,
     ) -> impl Iterator<Item = SubnetId> {
         // The bits of the node-id we are using to define the subnets.
-        let prefix_bits = spec.attestation_subnet_prefix_bits as u64;
+        let prefix_bits = spec.attestation_subnet_prefix_bits as u32;
 
         let node_id = U256::from_be_slice(&raw_node_id);
         // calculate the prefixes used to compute the subnet and shuffling