Merge "Make "dumpsys tethering" print the number of registered callbacks." am: 1e50b3ea24 am: 2d4eb7e18d

Original change: https://android-review.googlesource.com/c/platform/packages/modules/Connectivity/+/1749480

Change-Id: Ia2351cde37d919b7dba7b609b556c08533a978ff