sys: transceiver: Provide an adapter to netapi module

Since netapi is aimed to replace tranceiver one day, but porting
efforts usally take a while, this commit aims to provide access via
transceiver as we are used to for radio/network drivers that already implement
netapi (e. g. uart_net in #1454).
tests: transceiver: netapi: nativenet: Provide transceiver adapter tests