Don't skip visiting non-tuple slice in `typing.Annotated` subscripts (#17201)

Fixes: #17196

## Summary

Skipping these nodes for malformed type expressions would lead to
incorrect semantic state, which can in turn mean we emit false positives
for rules like `unused-variable`(`F841`)

## Test Plan

`cargo nextest run`

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

@@ -1669,7 +1669,15 @@ impl<'a> Visitor<'a> for Checker<'a> {
                                 }
                                 self.visit_expr_context(ctx);
                             } else {
-                                debug!("Found non-Expr::Tuple argument to PEP 593 Annotation.");
+                                if self.semantic.in_type_definition() {
+                                    // this should potentially trigger some kind of violation in the
+                                    // future, since it would indicate an invalid type expression
+                                    debug!("Found non-Expr::Tuple argument to PEP 593 Annotation.");
+                                }
+                                // even if the expression is invalid as a type expression, we should
+                                // still visit it so we don't accidentally treat variables as unused
+                                self.visit_expr(slice);
+                                self.visit_expr_context(ctx);
                             }
                         }
                         Some(typing::SubscriptKind::TypedDict) => {

crates/ruff_linter/src/rules/pyflakes/mod.rs

@@ -4263,4 +4263,22 @@ lambda: fu
             &[],
         );
     }
+
+    #[test]
+    fn gh_issue_17196_regression_test() {
+        flakes(
+            r#"
+            from typing import Annotated
+
+            def type_annotations_from_tuple():
+                annos = (str, "foo", "bar")
+                return Annotated[annos]
+
+            def type_annotations_from_filtered_tuple():
+                annos = (str, None, "foo", None, "bar")
+                return Annotated[tuple([a for a in annos if a is not None])]
+        "#,
+            &[],
+        );
+    }
 }