Type Mismatch in Network Fields Using configVariable

[schaable]

When using configVariable("variable_name") from hardhat-keystore in network configurations like url and accounts, TypeScript throws an error: Type 'ConfigurationVariable' is not assignable to type ...

For example:

networks: {
  myNetwork: {
    ...
    url: configVariable('OP_SEPOLIA_URL') // Type 'ConfigurationVariable' is not assignable to type 'string'.
  }
}

We should update sensitive fields types to accept the ConfigurationVariable type.