tests: drivers: can: filter out tests if zephyr,canbus not enabled

- Filter out the CAN controller driver tests if no zephyr,canbus chosen
  node is enabled in the devicetree.
- Rename the tests to follow the general test naming scheme.
- Remove the dedicated test selection for native_posix boards

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