[red-knot] Fix panic related to f-strings in annotations (#14613)

## Summary

Fix panics related to expressions without inferred types in invalid
syntax examples like:
```py
x: f"Literal[{1 + 2}]" = 3
```
where the `1 + 2` expression (and its sub-expressions) inside the
annotation did not have an inferred type.

## Test Plan

Added new corpus test.

crates/red_knot_python_semantic/src/types/infer.rs

@@ -4229,6 +4229,7 @@ impl<'db> TypeInferenceBuilder<'db> {
                     "annotation-f-string",
                     format_args!("Type expressions cannot use f-strings"),
                 );
+                self.infer_fstring_expression(fstring);
                 Type::Unknown
             }