[perflint] Simplify finding the loop target in PERF401 (#15025)

Fixes #15012.

```python
def f():
    # panics when the code can't find the loop variable
    values = [1, 2, 3]
    result = []
    for i in values:
        result.append(i + 1)
    del i
```

I'm not sure exactly why this test case panics, but I suspect the `del
i` removes the binding from the semantic model's symbols.

I changed the code to search for the correct binding by directly
iterating through the bindings. Since we know exactly which binding we
want, this should find the loop variable without any complications.

crates/ruff_linter/resources/test/fixtures/perflint/PERF401.py

@@ -244,3 +244,10 @@ def f():
         for a in values:
             result.append(a + 1)  # PERF401
     result = []
+
+def f():
+    values = [1, 2, 3]
+    result = []
+    for i in values:
+        result.append(i + 1)  # Ok
+    del i

crates/ruff_linter/src/rules/perflint/rules/manual_list_comprehension.rs

@@ -237,31 +237,12 @@ pub(crate) fn manual_list_comprehension(checker: &mut Checker, for_stmt: &ast::S
     // filtered = [x for x in y]
     // print(x)
     // ```
-    let last_target_binding = checker
+    let target_binding = checker
         .semantic()
-        .lookup_symbol(for_stmt_target_id)
-        .expect("for loop target must exist");
-
-    let target_binding = {
-        let mut bindings = [last_target_binding].into_iter().chain(
-            checker
-                .semantic()
-                .shadowed_bindings(checker.semantic().scope_id, last_target_binding)
-                .filter_map(|shadowed| shadowed.same_scope().then_some(shadowed.shadowed_id())),
-        );
-
-        bindings
-            .find_map(|binding_id| {
-                let binding = checker.semantic().binding(binding_id);
-                binding
-                    .statement(checker.semantic())
-                    .and_then(ast::Stmt::as_for_stmt)
-                    .is_some_and(|stmt| stmt.range == for_stmt.range)
-                    .then_some(binding)
-            })
-            .expect("for target binding must exist")
-    };
-
+        .bindings
+        .iter()
+        .find(|binding| for_stmt.target.range() == binding.range)
+        .unwrap();
     // If any references to the loop target variable are after the loop,
     // then converting it into a comprehension would cause a NameError
     if target_binding

crates/ruff_linter/src/rules/perflint/snapshots/ruff_linter__rules__perflint__tests__preview__PERF401_PERF401.py.snap

@@ -484,3 +484,5 @@ PERF401.py:245:13: PERF401 [*] Use `list.extend` to create a transformed list
 245     |-            result.append(a + 1)  # PERF401
     244 |+        result.extend(a + 1 for a in values)  # PERF401
 246 245 |     result = []
+247 246 | 
+248 247 | def f():