framework.jar - include framework-wifi-stubs instead of framework-wifi (Attempt 2)

Stop exporting @hide APIs from framework-wifi
to framework.jar by including framework-wifi-stubs
instead. At this point no code is allowed to call @hide APIs
defined in framework-wifi unless they have an explicit
exemption.

Attempt 1 broke the build, trying again.

Bug: 140299412
Change-Id: I3eecb0a5f6b1c0be85d684d190465d591994d99f
Test: boots up and connects to Wifi