Closes#7467.
This PR primarily addresses [the P2P changes](https://github.com/ethereum/EIPs/pull/9840) in [fusaka-devnet-2](https://fusaka-devnet-2.ethpandaops.io/). Specifically:
* [the new `nfd` parameter added to the `ENR`](https://github.com/ethereum/EIPs/pull/9840)
* [the modified `compute_fork_digest()` changes for every BPO fork](https://github.com/ethereum/EIPs/pull/9840)
90% of this PR was absolutely hacked together as fast as possible during the Berlinterop as fast as I could while running between Glamsterdam debates. Luckily, it seems to work. But I was unable to be as careful in avoiding bugs as I usually am. I've cleaned up the things *I remember* wanting to come back and have a closer look at. But still working on this.
Progress:
* [x] get it working on `fusaka-devnet-2`
* [ ] [*optional* disconnect from peers with incorrect `nfd` at the fork boundary](https://github.com/ethereum/consensus-specs/pull/4407) - Can be addressed in a future PR if necessary
* [x] first pass clean-up
* [x] fix up all the broken tests
* [x] final self-review
* [x] more thorough review from people more familiar with affected code
Closes#7167
- Ensure the fork digest is generated from ther light client updates attested header and not the signature slot
- Ensure the format of the SSZ response is spec compliant
* persist light client updates
* update beacon chain to serve light client updates
* resolve todos
* cache best update
* extend cache parts
* is better light client update
* resolve merge conflict
* initial api changes
* add lc update db column
* fmt
* added tests
* add sim
* Merge branch 'unstable' of https://github.com/sigp/lighthouse into persist-light-client-updates
* fix some weird issues with the simulator
* tests
* Merge branch 'unstable' of https://github.com/sigp/lighthouse into persist-light-client-updates
* test changes
* merge conflict
* testing
* started work on ef tests and some code clean up
* update tests
* linting
* noop pre altair, were still failing on electra though
* allow for zeroed light client header
* Merge branch 'unstable' of https://github.com/sigp/lighthouse into persist-light-client-updates
* merge unstable
* remove unwraps
* remove unwraps
* fetch bootstrap without always querying for state
* storing bootstrap parts in db
* mroe code cleanup
* test
* prune sync committee branches from dropped chains
* Update light_client_update.rs
* merge unstable
* move functionality to helper methods
* refactor is best update fn
* refactor is best update fn
* improve organization of light client server cache logic
* fork diget calc, and only spawn as many blcoks as we need for the lc update test
* resovle merge conflict
* add electra bootstrap logic, add logic to cache current sync committee
* add latest sync committe branch cache
* fetch lc update from the cache if it exists
* fmt
* Fix beacon_chain tests
* Add debug code to update ranking_order ef test
* Fix compare code
* merge conflicts
* merge conflict
* add better error messaging
* resolve merge conflicts
* remove lc update from basicsim
* rename sync comittte variable and fix persist condition
* refactor get_light_client_update logic
* add better comments, return helpful error messages over http and rpc
* pruning canonical non checkpoint slots
* fix test
* rerun test
* update pruning logic, add tests
* fix tests
* fix imports
* fmt
* refactor db code
* Refactor db method
* Refactor db method
* add additional comments
* Merge branch 'unstable' of https://github.com/sigp/lighthouse into persist-light-client-bootstrap
* fix merge
* linting
* merge conflict
* prevent overflow
* enable lc server for http api tests
* fix tests
* remove prints
* remove warning
* revert change
* persist light client updates
* update beacon chain to serve light client updates
* resolve todos
* cache best update
* extend cache parts
* is better light client update
* resolve merge conflict
* initial api changes
* add lc update db column
* fmt
* added tests
* add sim
* Merge branch 'unstable' of https://github.com/sigp/lighthouse into persist-light-client-updates
* fix some weird issues with the simulator
* tests
* Merge branch 'unstable' of https://github.com/sigp/lighthouse into persist-light-client-updates
* test changes
* merge conflict
* testing
* started work on ef tests and some code clean up
* update tests
* linting
* noop pre altair, were still failing on electra though
* allow for zeroed light client header
* Merge branch 'unstable' of https://github.com/sigp/lighthouse into persist-light-client-updates
* merge unstable
* remove unwraps
* remove unwraps
* Update light_client_update.rs
* merge unstable
* move functionality to helper methods
* refactor is best update fn
* refactor is best update fn
* improve organization of light client server cache logic
* fork diget calc, and only spawn as many blcoks as we need for the lc update test
* fetch lc update from the cache if it exists
* fmt
* Fix beacon_chain tests
* Add debug code to update ranking_order ef test
* Fix compare code
* merge conflicts
* fix test
* Merge branch 'persist-light-client-updates' of https://github.com/eserilev/lighthouse into persist-light-client-updates
* Use blinded blocks for light client proofs
* fix ef test
* merge conflicts
* fix lc update check
* Lint
* resolve merge conflict
* Merge branch 'persist-light-client-updates' of https://github.com/eserilev/lighthouse into persist-light-client-updates
* revert basic sim
* small fix
* revert sim
* Review PR
* resolve merge conflicts
* Merge branch 'unstable' into persist-light-client-updates
