Description

Add tests for the following light client ReqResp interfaces:

• GetLightClientBootstrap
• LightClientUpdatesByRange
• GetLightClientOptimisticUpdate
• GetLightClientFinalityUpdate

There are some existing tests written on this old branch, which relies on a mock_light_client. This mock is now obsolete due to breaking changes from libp2p and needs to be reworked.

The mock light client approach is a bit maintenance heavy, so we think it would be better to implement symmetric protocols (sending outbound light client requests) within the lighthouse-network crate. See this comment.