precompile-utils refactor

[nanocryk]

What does it do?

Refactor precompile-utils in preparation of migrating it into frontier.

Crate is re-organized to group features by domain:

• solidity: Conventions related to the Solidity language or ABI
  • codec: Solidity data encoding, old ::data. EvmData/EvmDataWriter/EvmDataReader are renamed into Codec/Writer/Reader, and are moved inside solidity::codec module. Codec is re-exported inside solidity which itself is included in the prelude, such that using the prelude allows to use solidity::Codec. Codec is not included directly in the prelude to avoid confusion with parity_scale_codec. Codec is both the trait and the derive macro. Reader and Writer are no longer re-exported in the prelude, instead functions like encode_arguments or decode_arguments should be used (with tuples for multiple values).
  • modifier: Checks related to view and payable keywords in Solidity.
  • revert: Allow generating more detailed error message that can include "backtraces" inside struct/array decoding.
• evm: Utils related more closely to EVM functionality
  • logs: Basic functions to create logs. A derive macro on structs would be better in the future.
  • handle: Contains an extension trait to add helpers on impl PrecompileHandle. Also contain an environmental used mainly to support re-entrancy with local XCM execution.
  • costs: few gas cost computation functions copied from the EVM. Should be made public instead inside the EVM itself.
• testing: Provide functions and mocks to more easily write precompile tests. As encoding has been largely improved execute_returns_encoded is shortened as execute_returns, while old execute_returns is renamed execute_returns_raw. There shouldn't be a need to use execute_returns_raw but I leave it just in case.
• substrate: Allows dispatching Substrate call with weight to gas convertion and proper gas checks and recording.
• precompile_set: Allows constructing a precompile set from other precompiles or precompile sets with opt-out security checks.

Left for future PRs

Implement derive macro from events.