Move precompiles into standalone library

[yperbasis]

Move precompiles into a standalone library https://github.com/torquem-ch/silkpre. That library has a C API.

Paweł wrote a suggestion on the C API for Ethereum precompile libraries. Currently the API of torquem-ch/silkpre is somewhat different, but later we can converge to the proposed API.

[codecov]

Codecov Report

Merging #628 (1e4452b) into master (3b43267) will decrease coverage by 0.51%.
The diff coverage is 90.16%.

@@            Coverage Diff             @@
##           master     #628      +/-   ##
==========================================
- Coverage   75.91%   75.39%   -0.52%     
==========================================
  Files         189      183       -6     
  Lines       13447    12465     -982     
  Branches     2162     2081      -81     
==========================================
- Hits        10208     9398     -810     
+ Misses       2347     2186     -161     
+ Partials      892      881      -11     

Impacted Files	Coverage Δ
core/silkworm/consensus/base/engine.cpp	90.90% <ø> (ø)
core/silkworm/execution/evm.hpp	80.00% <ø> (ø)
...ilkworm/stagedsync/stage_senders/recovery_farm.cpp	54.27% <0.00%> (ø)
...kworm/stagedsync/stage_senders/recovery_worker.hpp	100.00% <ø> (+50.00%)	⬆️
...kworm/stagedsync/stage_senders/recovery_worker.cpp	54.54% <50.00%> (-4.98%)	⬇️
core/silkworm/execution/evm.cpp	93.12% <95.65%> (-0.69%)	⬇️
core/silkworm/consensus/engine.cpp	98.07% <100.00%> (ø)
core/silkworm/types/transaction.cpp	82.10% <100.00%> (+0.23%)	⬆️
core/silkworm/types/y_parity_and_chain_id.cpp	100.00% <100.00%> (ø)
core/silkworm/state/intra_block_state.cpp	93.99% <0.00%> (-1.42%)	⬇️
... and 6 more

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[chfast]

Hi, I actually started playing with the C API today. I should be able to share some results maybe tomorrow. WIP: https://github.com/torquem-ch/silkpre/compare/capi.

I try to separate core functionality from gas cost so this can be used without heap allocated buffer. The nice C++ API could be build on top of it with gas cost so this becomes hourglass pattern.

Don't you have issue with diamond dependency of secp256k1?

[yperbasis]

Don't you have issue with diamond dependency of secp256k1?

Silkworm depends on silkpre, which in turns depends on secp256k1, so no diamond dependency. I've removed secp256k1 submodule from Silkworm.