Change stopwatch accuracy from milliseconds to microseconds

The microsecond time information needs to be recorded in
the NetworkStack Metrics (NetworkIpProvisioningReported).
So the unit of stopwatch is converted from millisecond to microsecond.

Bug: 151926185
Test: atest com.android.server.connectivity.NetworkMonitorTest
Original-Change: https://android-review.googlesource.com/1299376
Merged-In: I5a27a3b1316c67bf076b2e490860385267358ef8
Change-Id: I5a27a3b1316c67bf076b2e490860385267358ef8
3 files changed