Add visibility for TetheringCoverageTests

1. NetworkStackTestsLib can be visible to TetheringCoverageTests
2. NetworkStackJarJarRules can be visible to
   TetheringIntegrationTestsDefaults
3. Remove uncessary lib "libartbase" because
   it's not visible to TetheringCoverageTests.

Bug: 148636687
Test: atest NetworkStackTests
      atest TetheringCoverageTests
Change-Id: I0e0d597a968f99f4a99c3d7ab014af4e144ab40f
diff --git a/tests/unit/Android.bp b/tests/unit/Android.bp
index 565a5cb..98351cd 100644
--- a/tests/unit/Android.bp
+++ b/tests/unit/Android.bp
@@ -59,7 +59,10 @@
     min_sdk_version: "29",
     defaults: ["NetworkStackTestsDefaults"],
     static_libs: ["NetworkStackApiStableLib"],
-    visibility: ["//packages/modules/NetworkStack/tests/integration"]
+    visibility: [
+        "//packages/modules/NetworkStack/tests/integration",
+        "//frameworks/base/packages/Tethering/tests/integration",
+    ]
 }
 
 android_test {
@@ -77,7 +80,6 @@
 java_defaults {
     name: "libnetworkstackutilsjni_deps",
     jni_libs: [
-        "libartbase",
         "libbacktrace",
         "libbase",
         "libbinder",