Add mergeForkBlock

[enriavil1]

mergeForkBlock corresponds to FORK_NEXT_VALUE of EIP-3675.

[codecov]

Codecov Report

Merging #614 (a3fac49) into master (dcb3e91) will decrease coverage by 0.00%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #614      +/-   ##
==========================================
- Coverage   81.65%   81.64%   -0.01%     
==========================================
  Files         167      167              
  Lines       13925    13928       +3     
==========================================
+ Hits        11370    11372       +2     
- Misses       2555     2556       +1     

Impacted Files	Coverage Δ
core/silkworm/chain/config.hpp	100.00% <ø> (ø)
core/silkworm/chain/config.cpp	96.00% <100.00%> (+0.09%)	⬆️
core/silkworm/state/intra_block_state.cpp	96.51% <0.00%> (-0.95%)	⬇️
core/silkworm/crypto/sha-256.c	51.74% <0.00%> (+0.49%)	⬆️

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[yperbasis]

Silkworm uses uint64 for block numbers. Why do you want to change it to uint256?

[enriavil1]

Silkworm uses uint64 for block numbers. Why do you want to change it to uint256?

To match Erigon using big int in terminalBlockNumber

[AndreaLanfranchi]

Silkworm uses uint64 for block numbers. Why do you want to change it to uint256?

To match Erigon using big int in terminalBlockNumber

And why Erigon uses such a huge var type ?
Isn't uint64 enough ? IMHO even a uint32 is more than abundant