Move VpnManagerServiceTest and VpnTest to frameworks

These unit tests are closely tied to the source code in
frameworks/base and were incorrectly placed in the connectivity
module. Also update the libraries visibility that are used by
the tests.

Test: atest FrameworksNetTests
Change-Id: I196c33a8bd5b5cdb9d42aea381e900681ff6d25e
diff --git a/service-t/Android.bp b/service-t/Android.bp
index 19850fd..779f354 100644
--- a/service-t/Android.bp
+++ b/service-t/Android.bp
@@ -75,6 +75,7 @@
         "com.android.tethering",
     ],
     visibility: [
+        "//frameworks/base/services/tests/VpnTests",
         "//frameworks/base/tests/vcn",
         "//packages/modules/Connectivity/service",
         "//packages/modules/Connectivity/tests:__subpackages__",