Change vm visibility to internal in StdAssertions and StdUtils

[smol-ninja]

Currently, the visibility of vm in StdAssertions and StdUtils is private which means it cannot be use by the derived contract.

forge-std/src/StdAssertions.sol

Line 8 in bb4ceea

Vm private constant vm = Vm(address(uint160(uint256(keccak256("hevm cheat code")))));

forge-std/src/StdUtils.sol

Line 17 in bb4ceea

VmSafe private constant vm = VmSafe(address(uint160(uint256(keccak256("hevm cheat code")))));

If we change it to internal, vm can be used directly with StdAssertions and StdUtils imports.

[mds1]

This will cause a solc Identifer already declared error because we define vm as internal in CommonBase which is used by Test and Script. If you don't want to inherit from Test and Script you can instead inherit from CommonBase

[smol-ninja]

Thank you @mds1 for your comment. That solves it.