wifi: add test target/directory for unit testing WiFi framework APIs

The existing tests for the WiFi frameworks API android.net.wifi are
copied from frameworks/opt/wifi/tests, and will be removed in
frameworks/opt/wifi/tests.

Bug: 31745421
Change-Id: I789e983bc7dd02b6c3fa6a982ca671347912be0f
Test: frameworks/base/wifi/runtests.sh
7 files changed