EVM: precompiled blake2f

Context

fix #4829 (closed)

Implements the precompiled contract 0x09 called blake2f. This contract is used for efficient verification of the Equihash PoW used in Zcash, making a BTC Relay-style SPV client possible on Ethereum.

Manually testing the MR

A few tests are implemented in precompiled.rs both for checking inputs and contract execution.

Checklist

• Document the interface of any function added or modified (see the coding guidelines)
• Document any change to the user interface, including configuration parameters (see node configuration)
• Provide automatic testing (see the testing guide).
• For new features and bug fixes, add an item in the appropriate changelog (docs/protocols/alpha.rst for the protocol and the environment, CHANGES.rst at the root of the repository for everything else).
• Select suitable reviewers using the Reviewers field below.
• Select as Assignee the next person who should take action on that MR

Closes #4829 (closed)