scripts: introduce list_hardware.py for listing of architectures and SoCs

The list_hardware.py script parses archs.yml in all <arch-root>/arch
folders and soc.yml in all <soc-root>/soc sub-folders.

The archs.yml and soc.yml are introduced with hw model v2.

Hw model v2 removes the need for architecture knowledge of the SoCs,
and as part of this makes multi-arch and multi-core SoCs possible.

Hw model v2 also allows for greater flexibility in arch and SoC
organization as they can be organized freely.

As example SoCs can be organized by vendors, architecture, or any other
way as the socs.yml contains the path to the location of the SoC,
instead of relying on a specific arch.

Signed-off-by: Torsten Rasmussen <Torsten.Rasmussen@nordicsemi.no>