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>

beacon_node/http_api/src/test_utils.rs

@@ -209,6 +209,7 @@ pub async fn create_api_server<T: BeaconChainTypes>(
             enabled: true,
             listen_port: port,
             data_dir: std::path::PathBuf::from(DEFAULT_ROOT_DIR),
+            enable_light_client_server: true,
             ..Config::default()
         },
         chain: Some(chain),