Update uid state used for bucketizing data in fg vs bg states.

Currently we are using PROCESS_STATE_BOUND_FOREGROUND_SERVICE to
decide whether to allow network access for an uid or not but
PROCESS_STATE_TOP is used for bucketizing data in fg vs bg states.
It's possible that even though user restricts background data uasge
for an app, the bg data usage amount displayed to the user is > 0.
As this could be confusing, use PROCESS_STATE_BOUND_FOREGROUND_SERVICE
for bucketizing in fg vs bg states too.

Bug: 63907204
Test: atest com.android.server.NetworkPolicyManagerServiceTest
Test: manual
Change-Id: Ib506e421043fbe1052b6d0068ebf01d288faba21