Allow SysUi to see the connectivity diagnostic callbacks

SysUi needs to see connectivity diagnostic callbacks to display
 "Checking for internet access..." -> "Connected" or "No internet access".

Bug: 307161342
Test: atest FrameworksNetTests, manually connect to a network without internet connectivity,
verify Internet Dialog doesn't get stuck showing
 "Checking for internet access..."

Change-Id: I86e2b852ff9e5dfbfc37ba711f477166b0ac6835