Add wifi tile toggle changes to WifiRepository

Add methods in WifiRepository for the planned wifi toggle to
1) Enable wifi
2) Pause wifi
3) Scan for wifi

We will also include a flow for the current expected toggle state, which
will be used in a future CL for optimistic UI updates.

Flag: com.android.systemui.qs_split_internet_tile

Bug: 201143076
Test: WIP
Change-Id: I1add85a5b00194ac9d7efb6a64d7740768be006b