[image_picker] Deprecate platform interface methods (#4520)

Deprecates all of the platform interface methods that have been replaced with newer variants.
diff --git a/packages/image_picker/image_picker_platform_interface/CHANGELOG.md b/packages/image_picker/image_picker_platform_interface/CHANGELOG.md
index bcba89b..fc3d604 100644
--- a/packages/image_picker/image_picker_platform_interface/CHANGELOG.md
+++ b/packages/image_picker/image_picker_platform_interface/CHANGELOG.md
@@ -1,3 +1,7 @@
+## 2.9.0
+
+* Formally deprecates all methods that have been replaced with newer variants.
+
 ## 2.8.0
 
 * Adds `getMedia` method.
diff --git a/packages/image_picker/image_picker_platform_interface/lib/src/platform_interface/image_picker_platform.dart b/packages/image_picker/image_picker_platform_interface/lib/src/platform_interface/image_picker_platform.dart
index 66c5d3b..a31fbba 100644
--- a/packages/image_picker/image_picker_platform_interface/lib/src/platform_interface/image_picker_platform.dart
+++ b/packages/image_picker/image_picker_platform_interface/lib/src/platform_interface/image_picker_platform.dart
@@ -37,8 +37,6 @@
     _instance = instance;
   }
 
-  // Next version of the API.
-
   /// Returns a [PickedFile] with the image that was picked.
   ///
   /// The `source` argument controls where the image comes from. This can
@@ -67,6 +65,7 @@
   /// in this call. You can then call [retrieveLostData] when your app relaunches to retrieve the lost data.
   ///
   /// If no images were picked, the return value is null.
+  @Deprecated('Use getImageFromSource instead.')
   Future<PickedFile?> pickImage({
     required ImageSource source,
     double? maxWidth,
@@ -95,6 +94,7 @@
   /// a warning message will be logged.
   ///
   /// If no images were picked, the return value is null.
+  @Deprecated('Use getMultiImageWithOptions instead.')
   Future<List<PickedFile>?> pickMultiImage({
     double? maxWidth,
     double? maxHeight,
@@ -119,6 +119,7 @@
   /// in this call. You can then call [retrieveLostData] when your app relaunches to retrieve the lost data.
   ///
   /// If no images were picked, the return value is null.
+  @Deprecated('Use getVideo instead.')
   Future<PickedFile?> pickVideo({
     required ImageSource source,
     CameraDevice preferredCameraDevice = CameraDevice.rear,
@@ -141,12 +142,11 @@
   /// See also:
   /// * [LostData], for what's included in the response.
   /// * [Android Activity Lifecycle](https://developer.android.com/reference/android/app/Activity.html), for more information on MainActivity destruction.
+  @Deprecated('Use getLostData instead.')
   Future<LostData> retrieveLostData() {
     throw UnimplementedError('retrieveLostData() has not been implemented.');
   }
 
-  /// This method is deprecated in favor of [getImageFromSource] and will be removed in a future update.
-  ///
   /// Returns an [XFile] with the image that was picked.
   ///
   /// The `source` argument controls where the image comes from. This can
@@ -175,6 +175,7 @@
   /// in this call. You can then call [getLostData] when your app relaunches to retrieve the lost data.
   ///
   /// If no images were picked, the return value is null.
+  @Deprecated('Use getImageFromSource instead.')
   Future<XFile?> getImage({
     required ImageSource source,
     double? maxWidth,
@@ -185,8 +186,6 @@
     throw UnimplementedError('getImage() has not been implemented.');
   }
 
-  /// This method is deprecated in favor of [getMultiImageWithOptions] and will be removed in a future update.
-  ///
   /// Returns a [List<XFile>] with the images that were picked.
   ///
   /// The images come from the [ImageSource.gallery].
@@ -205,6 +204,7 @@
   /// a warning message will be logged.
   ///
   /// If no images were picked, the return value is null.
+  @Deprecated('Use getMultiImageWithOptions instead.')
   Future<List<XFile>?> getMultiImage({
     double? maxWidth,
     double? maxHeight,
diff --git a/packages/image_picker/image_picker_platform_interface/pubspec.yaml b/packages/image_picker/image_picker_platform_interface/pubspec.yaml
index 67a5070..3c51cb1 100644
--- a/packages/image_picker/image_picker_platform_interface/pubspec.yaml
+++ b/packages/image_picker/image_picker_platform_interface/pubspec.yaml
@@ -4,7 +4,7 @@
 issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+image_picker%22
 # NOTE: We strongly prefer non-breaking changes, even at the expense of a
 # less-clean API. See https://flutter.dev/go/platform-interface-breaking-changes
-version: 2.8.0
+version: 2.9.0
 
 environment:
   sdk: ">=2.18.0 <4.0.0"