[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>

crates/ruff_linter/src/checkers/ast/mod.rs

@@ -616,7 +616,8 @@ impl SemanticSyntaxContext for Checker<'_> {
             | SemanticSyntaxErrorKind::DuplicateMatchClassAttribute(_)
             | SemanticSyntaxErrorKind::InvalidStarExpression
             | SemanticSyntaxErrorKind::AsyncComprehensionInSyncComprehension(_)
-            | SemanticSyntaxErrorKind::DuplicateParameter(_) => {
+            | SemanticSyntaxErrorKind::DuplicateParameter(_)
+            | SemanticSyntaxErrorKind::NonlocalDeclarationAtModuleLevel => {
                 if self.settings.preview.is_enabled() {
                     self.semantic_errors.borrow_mut().push(error);
                 }