Add formatters/linters for solidity code

[sveitser]

Foundry's forge fmt that we use at the moment doesn't do much formatting. We previously used prettier with solidity plugin, solhint and slither. I think prettier and solhint would be a good start, unless something better appeared in the last year.

• [x] ~Add pnpm to nix shell.~: solhint and prettier are installed with nix.
• [x] ~Add pnpm i to shellHook (if it's not too slow).~
• [x] Add formatter (prettier).
• [x] ~Run prettier on solidity code.~: keep using cargo fmt.
• [x] Add linter (solhint).
• [x] Run solhint --fix on solidity code. Fix remaining errors by hand.
• [x] Add pre-commit hooks for formatting and linting.
• [x] Add checks to CI. We can also make the linting step in the CI use nix, this makes the pre-commit hooks easier to stay in sync with the CI.

At first glance the template https://github.com/paulrberg/foundry-template looks good. We can borrow from there.

We also used the tools in CAPE but since we haven't maintained that code base in a year I think borrowing from foundry-template is the better option.

_Originally posted by @sveitser in https://github.com/EspressoSystems/espresso-sequencer/pull/292#discussion_r1173520750_

[sveitser]

We can potentially borrow stuff from https://github.com/paulrberg/foundry-template