API for LightClientBootstrap, LightClientFinalityUpdate, LightClientOptimisticUpdate and light client events (#3954)

* rebase and add comment

* conditional test

* test

* optimistic chould be working now

* finality should be working now

* try again

* try again

* clippy fix

* add lc bootstrap beacon api

* add lc optimistic/finality update to events

* fmt

* That error isn't occuring on my computer but I think this should fix it

* Add missing test file

* Update light client types to comply with Altair light client spec.

* Fix test compilation

* Support deserializing light client structures for the Bellatrix fork

* Move `get_light_client_bootstrap` logic to `BeaconChain`. `LightClientBootstrap` API to return `ForkVersionedResponse`.

* Misc fixes.
- log cleanup
- move http_api config mutation to `config::get_config` for consistency
- fix light client API responses

* Add light client bootstrap API test and fix existing ones.

* Fix test for `light-client-server` http api config.

* Appease clippy

* Efficiency improvement when retrieving beacon state.

---------

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

consensus/state_processing/src/upgrade/altair.rs

@@ -54,7 +54,7 @@ pub fn upgrade_to_altair<E: EthSpec>(
         VariableList::new(vec![ParticipationFlags::default(); pre.validators.len()])?;
     let inactivity_scores = VariableList::new(vec![0; pre.validators.len()])?;
 
-    let temp_sync_committee = Arc::new(SyncCommittee::temporary()?);
+    let temp_sync_committee = Arc::new(SyncCommittee::temporary());
 
     // Where possible, use something like `mem::take` to move fields from behind the &mut
     // reference. For other fields that don't have a good default value, use `clone`.