@EnforcePermission migrations - NetworkPolicyManagerService

Migrates call sites to use the @EnforcePermission annotation
instead of manually checking permissions.

These are fully behavior-preserving changes that can be identified by
Android Lint (see SimpleManualPermissionEnforcementDetector)

Bug: 265014041
Test: TH
Change-Id: I1b81a760374a7ff249e9bf00f79341396336cd86