fix: add Block functions

[twoeths]

Motivation

• we miss Block functions, that causes us to use SignedBlock everywhere
• this is also not consistent to lodestar
• it'll likely a blocker for spec test

Description

• move functions from SignedBlock to Block, ensure the functions have the same signatures to the current lodestar
• no pointer on wrapped enums because we already have pointers in embedded enumbs
  • instead of

pub const SignedBlock = union(enum) {
   regular: *const SignedBeaconBlock,
   blinded: *const SignedBlindedBeaconBlock,
}

• this PR changes to

pub const SignedBlock = union(enum) {
    regular: SignedBeaconBlock,
    blinded: SignedBlindedBeaconBlock,
}

because the last level already includes pointers

pub const SignedBeaconBlock = union(enum) {
    phase0: *const ssz.phase0.SignedBeaconBlock.Type,
    altair: *const ssz.altair.SignedBeaconBlock.Type,
    bellatrix: *const ssz.bellatrix.SignedBeaconBlock.Type,
    capella: *const ssz.capella.SignedBeaconBlock.Type,
    deneb: *const ssz.deneb.SignedBeaconBlock.Type,
    electra: *const ssz.electra.SignedBeaconBlock.Type,

• no need pointer in wrapped enum types, ie use Block instead of *const Block in function signatures because we already have pointers inside the last level

pub const BeaconBlock = union(enum) {
    phase0: *const ssz.phase0.BeaconBlock.Type,
    altair: *const ssz.altair.BeaconBlock.Type,
    bellatrix: *const ssz.bellatrix.BeaconBlock.Type,
    capella: *const ssz.capella.BeaconBlock.Type,
    deneb: *const ssz.deneb.BeaconBlock.Type,
    electra: *const ssz.electra.BeaconBlock.Type,

Closes #50