[image_picker] Updates min SDK to 3.29 (flutter#9830)

For the `image_picker` packages:
- Updates the min SDK version to 3.29
- Runs the autoformatter with the new format
- Update code excerpts

This does not update versions because pushing format changes (even in READMEs) isn't worth doing a release that drops an SDK version (which we don't normally version)

Prep for flutter#9816

Author: stuartmorgan-g

packages/image_picker/image_picker/CHANGELOG.md

@@ -1,3 +1,7 @@
+## NEXT
+
+* Updates minimum supported SDK version to Flutter 3.29/Dart 3.7.
+
 ## 1.2.0
 
 * Adds `pickMultiVideo` to allow selecting multiple videos from the gallery.

packages/image_picker/image_picker/README.md

@@ -124,16 +124,18 @@ import 'package:image_picker_platform_interface/image_picker_platform_interface.
 // ···
 class MyCameraDelegate extends ImagePickerCameraDelegate {
   @override
-  Future<XFile?> takePhoto(
-      {ImagePickerCameraDelegateOptions options =
-          const ImagePickerCameraDelegateOptions()}) async {
+  Future<XFile?> takePhoto({
+    ImagePickerCameraDelegateOptions options =
+        const ImagePickerCameraDelegateOptions(),
+  }) async {
     return _takeAPhoto(options.preferredCameraDevice);
   }
 
   @override
-  Future<XFile?> takeVideo(
-      {ImagePickerCameraDelegateOptions options =
-          const ImagePickerCameraDelegateOptions()}) async {
+  Future<XFile?> takeVideo({
+    ImagePickerCameraDelegateOptions options =
+        const ImagePickerCameraDelegateOptions(),
+  }) async {
     return _takeAVideo(options.preferredCameraDevice);
   }
 }
@@ -172,8 +174,9 @@ final XFile? image = await picker.pickImage(source: ImageSource.gallery);
 // Capture a photo.
 final XFile? photo = await picker.pickImage(source: ImageSource.camera);
 // Pick a video.
-final XFile? galleryVideo =
-    await picker.pickVideo(source: ImageSource.gallery);
+final XFile? galleryVideo = await picker.pickVideo(
+  source: ImageSource.gallery,
+);
 // Capture a video.
 final XFile? cameraVideo = await picker.pickVideo(source: ImageSource.camera);
 // Pick multiple images.