Update FileSecurity class to copy files from scaffold directory

Not sure it's possible for the scaffold files to live in core/assets/scaffold as per this README in core/lib/Drupal/Component:

Each Component should be in its own namespace, and should be as self-contained
as possible.  It should be possible to split a Component off to its own
repository and use as a stand-alone library, independently of Drupal.

So for now I've put the files inside the component directory.

Looks like there are a few places in core that try to read from FileSecurity::htaccessLines(). Back to NW.