Add support for EIP-7939 CLZ

[Vectorized]

Abstract

EIP-7939 (CLZ) is an opcode that is scheduled for inclusion in the Fusaka hardfork.

https://eips.ethereum.org/EIPS/eip-7607#core-eips

Motivation

Support for the CLZ opcode.

Specification

The mathematical specification is outlined in the EIP.

Minimally, expose the clz opcode in inline-assembly (and pure yul).

Optionally, expose it in regular Solidity. However, this includes the added risk of breaking existing codebases which have a clz identifier in regular Solidity namespace.

As most existing use-cases of clz are in low level inline-assembly, implementing it just for inline-assembly may suffice.

Backwards Compatibility

Existing codebases which use clz as an identifier may break.