Create constants and data types

[Wizdave97]

Create all constants and data types as part of the light-client-primitives crate.

[dharjeezy]

Most of the constants and data types are already implemented here. The no-std implementation of the ethereum-consensus repo is implemented here and a PR for this can be found here.

There are other types spec'd out with the research carried out by @seunlanlege in the article which can be found here.

The other types and constants spec'd out are what needs to be created. Types such as:

• ExecutionPayloadProof
• BlockRootsProof
• AncestryProof
• AncestorBlock
• SyncCommitteeUpdate
• LightClientState
• LightClientUpdate