fix(transformer/es2018/for-await): hoist for-await generated bindings (#22355)

`for await` lowering emits several temporary bindings as `var`, but the transformer was registering those generated symbols in the current block scope instead of the nearest hoist scope.

For example, this input:

```js
async function* f(iter) {
  {
    for await (const value of iter) {
      value;
    }
  }
}
```

is lowered into code shaped like this:

```js
async function* f(iter) {
  {
    var _iteratorAbruptCompletion = false;
    var _didIteratorError = false;
    var _iteratorError;

    try {
      for (
        var _iterator = _asyncIterator(iter), _step;
        //  ^^^^^^^^^                         ^^^^^
        //  These are `var` declarations, so semantically they belong to
        //  the function/hoist scope, not the inner block scope.
        _iteratorAbruptCompletion = !(_step = await _iterator.next()).done;
        _iteratorAbruptCompletion = false
      ) {
        const value = _step.value;
        value;
      }
    } catch (err) {
      _didIteratorError = true;
      _iteratorError = err;
    }
  }
}
```

Before this PR, the AST transform generated the right JavaScript, but its semantic metadata recorded `_iterator`, `_step`, `_didIteratorError`, `_iteratorError`, and `_iteratorAbruptCompletion` in the current block scope:

That made the transformed semantic data disagree with semantic data rebuilt from the emitted AST.

crates/oxc_transformer/src/es2018/async_generator_functions/for_await.rs

@@ -102,8 +102,11 @@ impl<'a> AsyncGeneratorFunctions<'a> {
         span: Span,
         ctx: &mut TraverseCtx<'a>,
     ) -> ArenaVec<'a, Statement<'a>> {
-        let step_key =
-            ctx.generate_uid("step", ctx.current_scope_id(), SymbolFlags::FunctionScopedVariable);
+        let step_key = ctx.generate_uid(
+            "step",
+            ctx.current_hoist_scope_id(),
+            SymbolFlags::FunctionScopedVariable,
+        );
         // step.value
         let step_value = Expression::from(ctx.ast.member_expression_static(
             SPAN,
@@ -205,7 +208,7 @@ impl<'a> AsyncGeneratorFunctions<'a> {
         span: Span,
         ctx: &mut TraverseCtx<'a>,
     ) -> ArenaVec<'a, Statement<'a>> {
-        let var_scope_id = ctx.current_scope_id();
+        let var_scope_id = ctx.current_hoist_scope_id();
 
         let iterator_had_error_key =
             ctx.generate_uid("didIteratorError", var_scope_id, SymbolFlags::FunctionScopedVariable);

tasks/coverage/snapshots/semantic_babel.snap

@@ -2,7 +2,7 @@ commit: 6402dbbf
 
 semantic_babel Summary:
 AST Parsed     : 2236/2236 (100.00%)
-Positive Passed: 2030/2236 (90.79%)
+Positive Passed: 2031/2236 (90.83%)
 semantic Error: tasks/coverage/babel/packages/babel-parser/test/fixtures/comments/decorators/decorators-after-export/input.js
 Symbol span mismatch for "C":
 after transform: SymbolId(0): Span { start: 65, end: 66 }
@@ -87,29 +87,6 @@ Symbol scope ID mismatch for "_await":
 after transform: SymbolId(3): ScopeId(2)
 rebuilt        : SymbolId(2): ScopeId(0)
 
-semantic Error: tasks/coverage/babel/packages/babel-parser/test/fixtures/es2026/async-explicit-resource-management/valid-await-using-comments/input.js
-Bindings mismatch:
-after transform: ScopeId(1): ["_usingCtx", "_usingCtx3", "_usingCtx4"]
-rebuilt        : ScopeId(3): ["_didIteratorError", "_iterator", "_iteratorAbruptCompletion", "_iteratorError", "_step", "_usingCtx", "_usingCtx3", "_usingCtx4"]
-Bindings mismatch:
-after transform: ScopeId(7): ["_didIteratorError", "_iterator", "_iteratorAbruptCompletion", "_iteratorError", "_step"]
-rebuilt        : ScopeId(16): []
-Symbol scope ID mismatch for "_iteratorAbruptCompletion":
-after transform: SymbolId(14): ScopeId(7)
-rebuilt        : SymbolId(13): ScopeId(3)
-Symbol scope ID mismatch for "_didIteratorError":
-after transform: SymbolId(13): ScopeId(7)
-rebuilt        : SymbolId(14): ScopeId(3)
-Symbol scope ID mismatch for "_iteratorError":
-after transform: SymbolId(15): ScopeId(7)
-rebuilt        : SymbolId(15): ScopeId(3)
-Symbol scope ID mismatch for "_iterator":
-after transform: SymbolId(16): ScopeId(7)
-rebuilt        : SymbolId(16): ScopeId(3)
-Symbol scope ID mismatch for "_step":
-after transform: SymbolId(11): ScopeId(7)
-rebuilt        : SymbolId(17): ScopeId(3)
-
 semantic Error: tasks/coverage/babel/packages/babel-parser/test/fixtures/es2026/async-explicit-resource-management/valid-for-using-binding-of-of/input.js
 Symbol reference IDs mismatch for "of":
 after transform: SymbolId(1): [ReferenceId(0)]

tasks/coverage/snapshots/semantic_test262.snap

@@ -2,53 +2,7 @@ commit: d0c1b455
 
 semantic_test262 Summary:
 AST Parsed     : 47095/47095 (100.00%)
-Positive Passed: 45450/47095 (96.51%)
-semantic Error: tasks/coverage/test262/test/built-ins/AsyncFromSyncIteratorPrototype/next/for-await-iterator-next-rejected-promise-close.js
-Bindings mismatch:
-after transform: ScopeId(4): []
-rebuilt        : ScopeId(4): ["_didIteratorError", "_iterator", "_iteratorAbruptCompletion", "_iteratorError", "_step"]
-Bindings mismatch:
-after transform: ScopeId(5): ["_didIteratorError", "_iterator", "_iteratorAbruptCompletion", "_iteratorError", "_step"]
-rebuilt        : ScopeId(5): []
-Symbol scope ID mismatch for "_iteratorAbruptCompletion":
-after transform: SymbolId(8): ScopeId(5)
-rebuilt        : SymbolId(5): ScopeId(4)
-Symbol scope ID mismatch for "_didIteratorError":
-after transform: SymbolId(7): ScopeId(5)
-rebuilt        : SymbolId(6): ScopeId(4)
-Symbol scope ID mismatch for "_iteratorError":
-after transform: SymbolId(9): ScopeId(5)
-rebuilt        : SymbolId(7): ScopeId(4)
-Symbol scope ID mismatch for "_iterator":
-after transform: SymbolId(10): ScopeId(5)
-rebuilt        : SymbolId(8): ScopeId(4)
-Symbol scope ID mismatch for "_step":
-after transform: SymbolId(5): ScopeId(5)
-rebuilt        : SymbolId(9): ScopeId(4)
-
-semantic Error: tasks/coverage/test262/test/built-ins/AsyncFromSyncIteratorPrototype/next/for-await-next-rejected-promise-close.js
-Bindings mismatch:
-after transform: ScopeId(4): []
-rebuilt        : ScopeId(4): ["_didIteratorError", "_iterator", "_iteratorAbruptCompletion", "_iteratorError", "_step"]
-Bindings mismatch:
-after transform: ScopeId(5): ["_didIteratorError", "_iterator", "_iteratorAbruptCompletion", "_iteratorError", "_step"]
-rebuilt        : ScopeId(5): []
-Symbol scope ID mismatch for "_iteratorAbruptCompletion":
-after transform: SymbolId(8): ScopeId(5)
-rebuilt        : SymbolId(5): ScopeId(4)
-Symbol scope ID mismatch for "_didIteratorError":
-after transform: SymbolId(7): ScopeId(5)
-rebuilt        : SymbolId(6): ScopeId(4)
-Symbol scope ID mismatch for "_iteratorError":
-after transform: SymbolId(9): ScopeId(5)
-rebuilt        : SymbolId(7): ScopeId(4)
-Symbol scope ID mismatch for "_iterator":
-after transform: SymbolId(10): ScopeId(5)
-rebuilt        : SymbolId(8): ScopeId(4)
-Symbol scope ID mismatch for "_step":
-after transform: SymbolId(5): ScopeId(5)
-rebuilt        : SymbolId(9): ScopeId(4)
-
+Positive Passed: 45452/47095 (96.51%)
 semantic Error: tasks/coverage/test262/test/language/arguments-object/cls-decl-async-private-gen-meth-args-trailing-comma-multiple.js
 Scope flags mismatch:
 after transform: ScopeId(2): ScopeFlags(StrictMode | Function)