Logs atom for data network validation

When network validation is completed, it is recorded in metrics.
Network validation begins when a request is received from QNS and
a response is recorded as success, failure, not supported, etc.

Bug: 327257377
Test: atest DataNetworkValidationStatsTest PersistAtomsStorageTest
Change-Id: Ib2db3bb340bd3048250111b83bea4526117c5a5a