Read through the specs and started building upon PoC.

Updates

• Started building upon the epbs branch in the Prysm client
• Created a draft PR#13046 based on the ethereum consensus specs
• Faced some issues compiling the gRPC files due to incompatibility of Bazel with MacOS

Next Steps
Improve upon the PR based on the review, see alternatives to compile the gRPC if not through already present scripts that uses Bazel.