docs: enhance documentation with NatSpec for all public functions

Related: https://github.com/foundry-rs/book/issues/1303

To do:

- [x] Interfaces https://github.com/foundry-rs/forge-std/pull/666
- [ ] Base.sol
- [ ] console.sol
- [ ] console2.sol
- [ ] safeconsole.sol
- [ ] Script.sol
- [x] StdAssertions.sol
- [x] StdChains.sol https://github.com/foundry-rs/forge-std/pull/860
- [x] StdCheats.sol https://github.com/foundry-rs/forge-std/pull/860
- [ ] StdError.sol
- [x] StdInvariant.sol
- [x] StdJson.sol https://github.com/foundry-rs/forge-std/pull/860
- [ ] StdMath.sol
- [x] StdStorage.sol https://github.com/foundry-rs/forge-std/pull/860
- [x] StdStyle.sol https://github.com/foundry-rs/forge-std/pull/860
- [x] StdToml.sol https://github.com/foundry-rs/forge-std/pull/860
- [ ] StdUtils.sol
- [ ] Test.sol
- [ ] Vm.sol

Goals:

- [x] Document all public facing functions with `@notice`
- [x] Mark private variables and functions with underscore prefix https://github.com/foundry-rs/forge-std/pull/861
- [ ] Unify layouts to follow common best practices of grouping storage variables
- [ ] Move internal functions up, private functions down
- [ ] Should not modify any user facing function or interface

This will make it easier to autogenerate documentation that we can then load into https://book.getfoundry.sh/reference/forge-std/ and keep it up to date