[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
             }
 

crates/red_knot_workspace/resources/test/corpus/95_annotation_fstring_invalid.py

@@ -0,0 +1 @@
+x: f"Literal[{1 + 2}]" = 3

crates/red_knot_workspace/tests/check.rs

@@ -272,7 +272,7 @@ const KNOWN_FAILURES: &[(&str, bool, bool)] = &[
     ("crates/ruff_linter/resources/test/fixtures/pyupgrade/UP039.py", true, false),
     // related to circular references in type aliases (salsa cycle panic):
     ("crates/ruff_python_parser/resources/inline/err/type_alias_invalid_value_expr.py", true, true),
-    // related to f-strings in annotations (invalid syntax)
+    // related to circular references in f-string annotations (invalid syntax)
     ("crates/ruff_linter/resources/test/fixtures/pyflakes/F821_15.py", true, true),
     ("crates/ruff_linter/resources/test/fixtures/pyflakes/F821_14.py", false, true),
 ];