* Move BlockHeaderWithProof content to content key selector 0
- Remove as content type with content key selector 4
- Replace regular block header with BlockHeaderWithProof at
content key selector 0
* Apply blockHeader content key also to bridge
* Add tests for header with proof generation and verification
Portal master accumulator was removed from the network specs as a
content type shared on the network, as since the merge this is
a finite accumulator (pre-merge only).
So in this PR the accumulator gets removed as network type and
gets instead baked into the library. Building it is done by
seperate tooling (eth_data_exporter).
Because of this a lot of extra code can be removed that was
located in history_network, content_db, portal_protocol, etc.
Also removed to option to build the accumulator at start-up
of fluffy as this takes several minutes making it not viable.
It can still be loaded from a provided file however.
The ssz accumulator file is for now stored in the recently
created portal-spec-tests repository.
- Let accumulator finish its last pre merge epoch (hash_tree_root
on incomplete epoch).
- Adjust code to use isPreMerge and remove isCurrentEpoch
- Split up tests to a set that runs with a mainnet merge block
number and a set that runs with a testing value.