samples: modules: canopennode: filter tests based on dts

- Filter out the CANopenNode tests if no zephyr,canbus chosen node is
  enabled in the devicetree.
- Enable the program download build-only test on all boards with the
  necessary fixed partions.
- Explicitly exclude boards without the needed flash support from the
  program download build-only test as these do not even pass Kconfig and
  thus fail to complete the twister filter stage.

Signed-off-by: Henrik Brix Andersen <hebad@vestas.com>