Use PermissionUtils

The checking permission methods on NetworkStack has migrated to
PermissionUtils. Let these methods refer to PermissionUtils but
still keep them because lots of frameworks modules are using
NetworkStack methods to check permission.

Also replace the NetworkStack#checkNetworkStackPermission to
PermissionUtils in CS.

Bug: 178352309
Test: atest FrameworksNetTests
Change-Id: Icd38aa17fe471b810978e21ea361c41719e7802d