Reland: Add attribution tags for VCN and VPN

Allows IKE library metrics to identify and log the system clients

This commit also updates VcnManagementServiceTest to mock
out createAttributionContext

Bug: 278943609
Test: manually verified the metrics
Test: CtsVcnTestCases, FrameworksVcnTests, Ikev2VpnTest,
      VpnManagerServiceTest, VpnTest
Change-Id: I8b326de0484f9c97eb1b12f27a792c5ebf35ba1e