gnrc_netif: move option_tested to default init function

[jia200x]

Contribution description

This PR moves the netdev specific options_tested to the gnrc_netif_default_init.
Although the current implementation of gnrc_netif is still dependent to netdev, this allows to encapsulate all netdev specific calls in the gnrc_netif_ops_t functions.

Testing procedure

Probably a compile test should suffice...

Issues/PRs references

Required by #18156

[PeterKietzmann]

I do not really see through the gnrc_netif.c file and its organization, and was not aware of options_tested. Could you maybe explain (at the example of openDSME) why you have to move that assertion?

[jia200x]

This option_tested variable simply asserts that the "test" for netdev device ran (usually called by netif->ops->init).
Therefore, it's a netdev specific thing.

In case of netdev-less GNRC netif implementations (e,g openDSME) this will simply assert because for obvious reasons netdev is not tested.