Allow use of __esModule as an identifier

[mcmire]

It is common when mocking modules in Jest tests to use a property of __esModule: true:

jest.mock('@metamask/eth-sig-util', () => {
  return {
    // eslint-disable-next-line @typescript-eslint/naming-convention
    __esModule: true,
    ...jest.requireActual('@metamask/eth-sig-util'),
  };
});

We should allow this as a property name so that we don't need an ESLint override.