Wificond: transfer implementation to android.net.wifi

Move implementation of wificond to frameworks/base (android.net.wifi)
in prepration for making into a public API (which will be a wrapper
around the AIDL).

Bug: 140062898
Test: atest com.android.server.wifi
Test: atest android.net.wifi
Test: associates, soft AP client information received correctly
Change-Id: I3c5ede95d0421a1e00078e0316e9a2e751156f3e