[NAN] Expose NAN characteristics as an API

Expose NAN characteristics as an API.

(cherry-pick of commit 3a9de10963d869fa8f721432ce12785de384c560)

Bug: 31912101
Test: build and validate API updates
Change-Id: If02942d738aab8fa2f2f47489c6840af1bc38280
4 files changed