On `ELECTRA_FORK_EPOCH`, PeerDAS is not yet activated, hence the current
mechanism based on `BlobSidecar` is still in use. With EIP-7688, the
generalized indices of `BeaconBlockBody` get reindexed, changing the
length of the inclusion proof within the `BlobSidecar`. Because network
Req/Resp operations allow responses across fork boundaries, this creates
the need for a `ForkedBlobSidecar` in that layer, same as already done
for `ForkedSignedBeaconBock` for similar reasons.
Note: This PR is only needed if PeerDAS is adopted _after_ EIP-7688.
If PeerDAS is adopted _before_ EIP-7688, a similar PR may be needed for
forked columns. Coincidental `Forked` jank can only be fully avoided if
both features activate at the same epoch, actual changes to blobs aside.
Delaying EIP-7688 for sole purpose of epoch alignemnt is not worth it.
* extend light client protocol for Electra
Add missing Electra support for light client protocol:
- https://github.com/ethereum/consensus-specs/pull/3811
Tested against PR consensus-spec-tests, the test runner automatically
picks up the new tests once available.
* workaround `version-2-0`: `Error: cannot instantiate: 'SomeUnsignedInt'`
* fix initialization when Electra not scheduled
* try reduce stack size in test
* put correct sync committee branch version into DB
* adjust fork schedule in light client data tests
* further reduce stack size
* split function into multiple parts
* rename variable
* regenerate test reports to cover new Electra tests
* add Nim bug reference
`sizeof` also includes padding between fields, while SSZ defines
`fixedPortionSize` (on type) or `sszSize` (on value) to denote
required bytes to encode. Switch forked block/state readers to SSZ size.
As blocks/states are much larger than the padding, this doesn't affect
practical use cases but is slightly more correct this way.
Extend slot start message and default status bar with information about
current head fork and the next fork transition (corresponding to head).
This is useful to know whether a synced client is aware of a future fork
and can also be useful when syncing from old forks to follow progress
across the various forks.
```
peers: 8 ❯ finalized: 741c2ce2:230474 ❯ head: b330f58b:230477:20 ❯ fork: Capella (next: Deneb:231680) ❯ time: 230599:24 (7379192) ❯ sync: 00h24m (99.63%) 2.6492slots/s (QwQUwQPQDQ:7375263)/opt
```
```
INF 2024-01-12 12:18:00.001+01:00 Slot start topics="beacnde" slot=7379190 epoch=230599 fork="Capella (next: Deneb:231680)" sync="--h--m (99.62%) 0.0000slots/s (wwwwwwwwww:7375167)/opt" peers=0 head=741c2ce2:7375168 finalized=230472:723abe7e delay=1ms861us
```
As followup from #5654, ensure that we still keep the comment around
referring to the correct `forkchoiceUpdated` to use being driven by
the fork schedule.
* use `PayloadAttributesV3` in `nimbus_light_client` for Deneb
From Deneb onward, `forkchoiceUpdated` requires `PayloadAttributesV3`.
In `nimbus_light_client` we still used `PayloadAttributesV2`.
Also clean up two other locations that were already correctly using
`PayloadAttributesV3`, to reduce code duplication.
* fix letter case