The stocks example app is outdated and deprecated, but we still use it for some benchmark tests. Moving it into the benchmarks directory to indicate its status.

* Revert "Update Hello World to latest iOS project template (#8634)"

This reverts commit 6dc6ed4e.

* Revert "Update Gallery to latest iOS project template (#8637)"

This reverts commit 84c42aac.

* Revert "Update Stocks to latest iOS project template (#8640)"

This reverts commit 90774c18.

We now use a different approach for ios projects where the developer controls
the Xcode project file. This patch removes the old ".generated" approach in
favor of the new approach.

This patch changes the default `flutter create` command to generate a
HelloServices-style app on iOS. As a consequence, the Atom integration now
fully works with HelloServices.

This example shows how to build a basic app using a custom Xcode project.
Future patches will bring the functionality up to par with hello_android.