Add Capella & Deneb light client support

## Description

Lighthouse's current light client support was implemented based on the Altair spec, and need to upgraded to conform to the Capella/Deneb light client specs:
- [Capella light client spec](https://github.com/ethereum/consensus-specs/tree/dev/specs/capella/light-client)
- [Deneb light client spec](https://github.com/ethereum/consensus-specs/tree/dev/specs/deneb/light-client)

