fix(cli): use os-specific invalid paths for tests

[CuriousCorrelation]

CLI test failing on trying to test for invalid paths

Initial Issue:

Test is for the CLI tool to verify how it behaves when attempting to export a report to an invalid path.
But, when running the test on Windows, it failed to pass the assertions in the test, even though the error output was as expected.

The Test:

  const args = `test ${COLL_PATH} --reporter-junit /non-existent-path/report.xml`;
  ...
  ...
  const out = getErrorCode(stderr);
  expect(out).toBe<HoppErrorCode>("REPORT_EXPORT_FAILED");
});

What Went Wrong:

• The test passed on most platforms, but not on Windows.
• The main issue occurred because we were checking for a specific error code in the stderr, but Windows returned something different in stderr - ENOENT

---

The Solution:

• On Windows, Z: would be an invalid drive letter (unless the drive is manually mapped, which it usually isn't).
• On Linux (or other Unix-like systems), / is the root path.
• Now both systems will have root path as the base for invalid paths.

const invalidPath = process.platform === 'win32'
  ? 'Z:/non-existent-path/report.xml'
  : '/non-existent/report.xml';

Closes HFE-647