[dart:js/js_util] Deprecate dart:js and dart:js_util

#59716

Deprecate these in favor of dart:js_interop. Modifies code
samples to account for the deprecated imports.

CoreLibraryReviewExempt: JS-specific library, deprecation only.
Change-Id: I9f01cd203212aaeca08aa1c5a4000b67f54756b9
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/401046
Reviewed-by: Sigmund Cherem <sigmund@google.com>
Reviewed-by: Kevin Moore <kevmoo@google.com>

CHANGELOG.md

@@ -241,6 +241,16 @@ AOT snapshot can be used as follows to run DDC <dart-sdk>/bin/dartaotruntime
   Users should migrate to using `dart:js_interop` and `package:web`. See
   [#59716][].
 
+#### `dart:js`
+
+- `dart:js` is marked deprecated and will be removed in an upcoming release.
+  Users should migrate to using `dart:js_interop`. See [#59716][].
+
+#### `dart:js_util`
+
+- `dart:js_util` is marked deprecated and will be removed in an upcoming
+  release. Users should migrate to using `dart:js_interop`. See [#59716][].
+
 [#59716]: https://github.com/dart-lang/sdk/issues/59716
 
 ## 3.6.0

sdk/lib/js/js.dart

@@ -84,6 +84,7 @@
 ///     var jsArray = JsObject.jsify([1, 2, 3]);
 ///
 /// {@category Web (Legacy)}
+@Deprecated('Use dart:js_interop instead.')
 library dart.js;
 
 import 'dart:collection' show ListMixin;

sdk/lib/js_util/js_util.dart

@@ -14,6 +14,7 @@
 /// with `@JS()` annotations.
 ///
 /// {@category Web (Legacy)}
+@Deprecated('Use dart:js_interop instead.')
 library dart.js_util;
 
 // Examples can assume:
@@ -148,7 +149,16 @@ class NullRejectionException implements Exception {
 
 /// Converts a JavaScript Promise to a Dart [Future].
 ///
-/// ```dart template:top
+/// ```dart
+/// // ignore: deprecated_member_use_from_same_package
+/// import 'dart:js_util';
+///
+/// // ignore: deprecated_member_use_from_same_package
+/// import 'package:js/js.dart';
+///
+/// @JS()
+/// class Promise<T> {}
+///
 /// @JS()
 /// external Promise<num> get threePromise; // Resolves to 3
 ///