Quoted altair fields (2.0) (#2712)

## Issue Addressed

Resolves #2689

## Proposed Changes

Copy of #2709 so I can appease CI and merge without waiting for @realbigsean to come online. See #2709 for more information.

## Additional Info

NA


Co-authored-by: realbigsean <seananderson33@gmail.com>

consensus/types/src/beacon_state.rs

@@ -266,6 +266,7 @@ where
     pub finalized_checkpoint: Checkpoint,
 
     // Inactivity
+    #[serde(with = "ssz_types::serde_utils::quoted_u64_var_list")]
     #[superstruct(only(Altair))]
     pub inactivity_scores: VariableList<u64, T::ValidatorRegistryLimit>,
 

consensus/types/src/participation_flags.rs

@@ -9,6 +9,7 @@ use tree_hash::{TreeHash, TreeHashType};
 #[serde(transparent)]
 #[cfg_attr(feature = "arbitrary-fuzz", derive(arbitrary::Arbitrary))]
 pub struct ParticipationFlags {
+    #[serde(with = "eth2_serde_utils::quoted_u8")]
     bits: u8,
 }