[syntax-errors] `nonlocal` declaration at module level (#17559)
## Summary
Part of #17412
Add a new compile-time syntax error for detecting `nonlocal`
declarations at a module level.
## Test Plan
- Added new inline tests for the syntax error
- Updated existing tests for `nonlocal` statement parsing to be inside a
function scope
Co-authored-by: Brent Westbrook <36778786+ntBre@users.noreply.github.com>
