Adds an empty privacy manifest, and commented out code to include it in the build, to the plugin template. This will make it much easier to explain how to add a privacy manifest in plugin docs, since instead of explaining the format of the file from scratch and providing example code to inculde it, we can just instruct people to add entries to an exisitng file and then uncomment a line or two. This will also make it much easier to figure out from the template output itself how to add support for people who don't find the documentation.
Part of https://github.com/flutter/flutter/issues/131940
Fixes https://github.com/flutter/flutter/issues/140013
When Swift Package Manager feature is enabled, create app and create plugin will have Swift Package Manager integration already added and will not need to undergo a migration.
Fixes https://github.com/flutter/flutter/issues/146371.
```
flutter config --enable-swift-package-manager
flutter create --ios-language swift --platforms ios,macos swift_app_name
flutter create --ios-language objc --platforms ios objc_app_name
flutter create --template=plugin --ios-language swift --platforms ios,macos swift_plugin_name
flutter create --template=plugin --ios-language objc --platforms ios objc_plugin_name
```
