device: Add device subsystem enumeration script

The device enumeration feature requires all devices
to place their API implementation in linker sections
by api type. This commit adds a script which uses
the tag __subsystem to identify all existing driver
API types and generate iterable sections for them.

The script is invoked from the top CMakeLists.txt

Signed-off-by: Bjarki Arge Andreasen <baa@trackunit.com>
Co-authored-by: Pieter De Gendt <pieter.degendt@basalte.be>
Signed-off-by: Pieter De Gendt <pieter.degendt@basalte.be>