* Update examples to lower the deployment target on iOS.

* Remove stray PRODUCT_BUNDLE_IDENTIFIER

This was erroneously added and overrides
the bundle for the gallery causing signing
to fail in my setup.

@chinmaygarde

* Remove PRODUCT_BUNDLE_IDENTIFIER from all Runner pbxproj's

We want to use the FlutterViewController in this new project template.

Fixes #4840

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.