[AWARE] Implement custom Wi-Fi Aware network specifier

Convert Wi-Fi Aware connectivity requests to use a custom
network specifier (as opposed to a string). Aside from
simplifying code, allows for more control of information
printed out, and of additional information to be packaged
and used in network decisions (uid - TBD).

(cherry-pick of commit a5028455)

Bug: 36275276
Bug: 36053921
Test: unit tests and integration (sl4a) tests passing.
Merged-In: I776fb348b15ec4830f890a8ac5c41f24594e12a7
Change-Id: I776fb348b15ec4830f890a8ac5c41f24594e12a7