Fix custody context initialization race condition that caused panic (#8391)

Take 2 of #8390.

Fixes the race condition properly instead of propagating the error. I think this is a better alternative, and doesn't seem to look that bad.


  * Lift node id loading or generation from `NetworkService ` startup to the `ClientBuilder`, so that it can be used to compute custody columns for the beacon chain without waiting for Network bootstrap.

I've considered and implemented a few alternatives:
1. passing `node_id` to beacon chain builder and compute columns when creating `CustodyContext`. This approach isn't good for separation of concerns and isn't great for testability
2. passing `ordered_custody_groups` to beacon chain. `CustodyContext` only uses this to compute ordered custody columns, so we might as well lift this logic out, so we don't have to do error handling in `CustodyContext` construction. Less tests to update;.


Co-Authored-By: Jimmy Chen <jchen.tc@gmail.com>

consensus/types/src/data_column_custody_group.rs

@@ -42,7 +42,7 @@ pub fn get_custody_groups(
 ///
 /// # Returns
 /// Vector of custody group indices in computation order or error if parameters are invalid
-pub fn get_custody_groups_ordered(
+fn get_custody_groups_ordered(
     raw_node_id: [u8; 32],
     custody_group_count: u64,
     spec: &ChainSpec,
@@ -76,6 +76,27 @@ pub fn get_custody_groups_ordered(
     Ok(custody_groups)
 }
 
+/// Returns a deterministically ordered list of custody columns assigned to a node,
+/// preserving the order in which they were computed during iteration.
+///
+/// # Arguments
+/// * `raw_node_id` - 32-byte node identifier
+/// * `spec` - Chain specification containing custody parameters
+pub fn compute_ordered_custody_column_indices<E: EthSpec>(
+    raw_node_id: [u8; 32],
+    spec: &ChainSpec,
+) -> Result<Vec<ColumnIndex>, DataColumnCustodyGroupError> {
+    let all_custody_groups_ordered =
+        get_custody_groups_ordered(raw_node_id, spec.number_of_custody_groups, spec)?;
+
+    let mut ordered_custody_columns = vec![];
+    for custody_index in all_custody_groups_ordered {
+        let columns = compute_columns_for_custody_group::<E>(custody_index, spec)?;
+        ordered_custody_columns.extend(columns);
+    }
+    Ok(ordered_custody_columns)
+}
+
 /// Returns the columns that are associated with a given custody group.
 ///
 /// spec: https://github.com/ethereum/consensus-specs/blob/8e0d0d48e81d6c7c5a8253ab61340f5ea5bac66a/specs/fulu/das-core.md#compute_columns_for_custody_group