Deneb PR feedback updates (#4716)

* move length update outside of if let in LRU cache

* add comment and use hex for G1_POINT_AT_INFINITY

* remove some misleading comments from `ssz_snappy`

* make sure we can't overflow on blobs by range requests with large counts

* downgrade gossip verification internal availability check error

* change blob rpc responses from BlockingFnWithManualSendOnIdle to BlockingFn

* remove unnecessary collect in blobs by range response

* add a comment to blobs by range response start slot logic

* typo persist_data_availabilty_checker -> persist_data_availability_checker

* unify cheap_state_advance_to_obtain_committees

beacon_node/beacon_chain/src/beacon_chain.rs

@@ -648,7 +648,7 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
         Ok(())
     }
 
-    pub fn persist_data_availabilty_checker(&self) -> Result<(), Error> {
+    pub fn persist_data_availability_checker(&self) -> Result<(), Error> {
         let _timer = metrics::start_timer(&metrics::PERSIST_DATA_AVAILABILITY_CHECKER);
         self.data_availability_checker.persist_all()?;
 
@@ -6298,7 +6298,7 @@ impl<T: BeaconChainTypes> Drop for BeaconChain<T> {
         let drop = || -> Result<(), Error> {
             self.persist_head_and_fork_choice()?;
             self.persist_op_pool()?;
-            self.persist_data_availabilty_checker()?;
+            self.persist_data_availability_checker()?;
             self.persist_eth1_cache()
         };