Wifi usability: Add @SystemApi to send Wifi usability stats

Add system API to allow framework to send Wifi usability stats to
system APK.
Also add a new permission to protect this API from being
used by unauthorized applications.
In addition, add a few more entries in Wifi.proto.

Bug: 113262380
Test: Unit tests for Wifi: frameworks/base/wifi/tests/runtests.sh

Change-Id: I5432419d6da3db96ecc6ff8e1c3197121ca7afbc
Signed-off-by: Mingguang Xu <mingguangxu@google.com>