[CHORE]: remove solc compilation and and use hardhat compile / instead

[artdgn]

We're using solc to compile in some places, and hardhat everywhere else:

• Refactor node publish build and node publish verify to rely on npx hardhat compile and npx hardhat verify.
• Remove solc dependency and custom code to these tasks.

This will enable e.g. compiling artifacts with different solidity versions, and will remove a lot of custom code.