Clean up VpnTest

- Reset any permissions to PERMISSION_DENIED in tearDown().
- Check there is only one category will be sent when VpnManager
  event is sent.
- Remove SDK check since VpnTest is non-connectivity-module-test
  now, which will not be run on mainline-prod target when running
  TH.
- Have two new methods for verifying ALWAYS_ON_STATE_CHANGED
  event and DEACTIVATED_BY_USER event, the new methods make the
  code clearer and more easy to read.
- Check if the target package of receiving VpnManager event is
  expected or not.
- Import recent ConstantsShim instead of a specific API version.

Bug: 236409954
Test: atest FrameworksNetTests:VpnTest
Change-Id: Ibe5d549f86d11d32e2f0ae63eab1d80ee8800e0d
2 files changed