wifi: Begin NAN iface methods implementation

Start implementation of the NAN iface HIDL methods by plumbing the HIDL
stubs to the corresponding legacy HAL methods. The incoming HIDL struct
needs to be converted to legacy for the HIDL methods. The legacy HAL
structs needs to be converted to HIDL for callbacks.

This CL only has a couple of methods and some structure conversion.
etan@ will take over the rest.

Bug: 31991076
Test: Compiles
Change-Id: Ide348f4c3318822226bb7de93d091107c7465cd3