Runtime rpc request sizes (#4841)

* add runtime variable list type

* add configs to ChainSpec

* git rid of max request blocks type

* fix tests and lints

* remove todos

* git rid of old const usage

* fix decode impl

* add new config to `Config` api struct

* add docs fix compilt

* move methods for per-fork-spec to chainspec

* get values off chain spec

* fix compile

* remove min by root size

* add tests for runtime var list

---------

Co-authored-by: Jimmy Chen <jchen.tc@gmail.com>

beacon_node/network/src/sync/network_context.rs

@@ -475,9 +475,15 @@ impl<T: BeaconChainTypes> SyncNetworkContext<T> {
         };
         let request_id = RequestId::Sync(sync_id);
 
-        if let Some(block_root) = blob_request.blob_ids.first().map(|id| id.block_root) {
+        if let Some(block_root) = blob_request
+            .blob_ids
+            .as_slice()
+            .first()
+            .map(|id| id.block_root)
+        {
             let indices = blob_request
                 .blob_ids
+                .as_slice()
                 .iter()
                 .map(|id| id.index)
                 .collect::<Vec<_>>();