run: rum: migrate to new net80211 encryption key API

Migrate to the new encryption key API rather than poking at the
key struct directly.

Locally tested:

• STA mode - run0: MAC/BBP RT2860 (rev 0x0101), RF RT2820 (MIMO 2T2R), address 00:0e:2e:e5:ae:3a

Differential Revision: https://reviews.freebsd.org/D54462