…ined in EIP PR 5707 (fee market update)

This also introduces an `ENABLE_WITHDRAWALS` feature-flag to allow
implementers test EIP-4844 without including Capella-specific state
changes.

Co-authored-by: Hsiao-Wei Wang <hsiaowei.eth@gmail.com>

And remove the ENABLE_WITHDRAWALS feature-flag. The Testing section in
the spec has been updated to specify how withdrawals is to be disabled

Co-authored-by: Alex Stokes <r.alex.stokes@gmail.com>

In light client tests, a variable is named `finality_header` but
everywhere else it is called `finalized_header`. Rename for consistency.

For LC gossip, the documentation did not specify what slot number to use
for deriving the gossip objects. This missing documentation is now added
to document using `attested_header.slot`.

A few LC functions were not yet updated to use a more concise function
for computing sync committee period for a slot. Updating to that func.

Add more detailed LC object documentation to explain that the various
merkle proofs are relative to the beacon block's state root.
Likewise, clarify that sync committees relate to the finalized header
(not to the optimistic header, which can be a period ahead).

Currently, `test_single_merkle_proof` only supports `BeaconState` tests.
For future tests, different object classes are desirable. Update format
to allow testing other objects as well.

Future light client tests will also incorporate execution payload data.
To avoid confusion, rename the current `root` check to `beacon_root`.
Doing this now, as #3066 already requires LC test runners to update.

Consistent variable name in LC test

Consistently use `compute_sync_committee_period_at_slot`

Clarify where LC proofs are rooted

Rename LC test check from `root` to `beacon_root`

`remerkleable` was updated to address potentially incorrect computation
of `hash_tree_root` against default-initialized `Vector` objects.
Switching to the fixed version.

Moving the `is_post_xxx` functions to a separate module allows `genesis`
to also use them (cyclic import from `context` prevented this before).
This allows removing `FORKS_BEFORE_ALTAIR` and `FORKS_BEFORE_BELLATRIX`
constants and adding a more general `is_post_fork` function that needs
less maintenance. This then allows definition of `with_all_phases_from`
to streamline the implementation of the `with_xxx_and_later` decorators.

EIP4844: Remove signed blobs

Document how to derive fork context for LC gossip

README.md: Fix broken links

Update `remerkleable` to 0.1.25

This commit changes the public API of the KZG library to the following high-level API:

```
- verify_kzg_proof()
- compute_aggregate_kzg_proof()
- verify_aggregate_kzg_proof()
- blob_to_kzg_commitment()
```

compared to the previous much more low-level API:

```
- compute_powers()
- matrix_lincomb()
- lincomb()
- bytes_to_bls_field()
- evaluate_polynomial_in_evaluation_form()
- verify_kzg_proof()
- compute_kzg_proof()
```

This means that all the cryptographic logic (including Fiat-Shamir) is now isolated and hidden in the KZG library and the `validator.md` file ends up being significantly simplified, only calling high-level KZG functions.

Some additional things that this commit does:

- Moves all EIP4844 cryptography into polynomial-commitments.md
- Improves the Fiat-Shamir stack by removing the need for SSZ and by introducing simple domain separators

Co-authored-by: Kevaundray Wedderburn <kevtheappdev@gmail.com>
Co-authored-by: Hsiao-Wei Wang <hsiaowei.eth@gmail.com>
Co-authored-by: Dankrad Feist <mail@dankradfeist.de>

…g building pyspec

- Implemented many of Alex's comments including reinsertion of the
  withdrawal index in the BeaconState
- Implemented Sean's suggestion of separating the logic for block
  production so that one matches the list in the payload with what
`get_expected_withdrawals` returns
- Changed `get_expected_wihdrawals` to match the current behavior and
  moved it to `beacon-chain.md`

Fix type error in the inputs to hash_to_bls_field()

Co-authored-by: Alex Stokes <r.alex.stokes@gmail.com>

Co-authored-by: Alex Stokes <r.alex.stokes@gmail.com>

Co-authored-by: Alex Stokes <r.alex.stokes@gmail.com>

Capella: Add Gossip Topic bls_to_execution_change

Fix typo in `bellatrix` p2p docs

…-block-packing

add note about packing BLS to execution changes into a block

eip4844: update tx_peek_blob_versioned_hashes to match tx type from fee market update

Rework the testing KZG trusted setups presets

EIP4844: Remove `DOMAIN_BLOBS_SIDECAR`

Co-authored-by: Alex Stokes <r.alex.stokes@gmail.com>

…nsus-specs into withdrawals_without_queues