Added support for OSU Provider provisioning action on click

Added a call to AccessPoint.startOsuProvisioning() to
onPreferenceTreeClick to open up an OSU provider flow when the user
clicks on an AccessPointPreference pertaining to an OSU provider
AccessPoint.

Bug: 118705403
Test: manual, build and tap on the OSU provider AP.
Change-Id: I3c321c2a6d2336a0cc92a30ae051146d2fc05fb7