Add permission check for CaptivePortal#reevaluateNetwork

CaptivePortal#reevaluateNetwork is added as a system API which
requires a proper permission check.

Bug: 148379628
Test: Manually check with captive portal
Test: atest FrameworksNetTests
Test: make test-api-stubs-docs-update-current-api \
      system-api-stubs-docs-update-current-api

Change-Id: I559d42089aeb09801d14c251c5165fca793c3cb3