Move socket tagging implementation to mainline.

Currently, socket tagging is implemented in the framework. The
Java code is in NetworkManagmentSocketTagger.java and the JNI is
in libandroid and loaded by the general framework JNI loader.

- Move the Java implementation to TrafficStats, which is the only
  caller of NetworkManagmentSocketTagger. This simplifies the
  code a bit because a number of methods can be deleted.

- Move the JNI code to a new JNI library in the APEX. The library
  depends only on the NDK and statically links the NDK-only
  version of libnativehelper. Its size is only 5k on ARM and 10k
  on ARM64.

- Temporarily make the framework depend on this library until the
  rest of the T connectivity code moves to the APEX.

Test: atest NetworkUsageStatsTest CtsNetTestCases:TrafficStatsTest
Change-Id: I050c7c515237f68b78d08987bc443f50a7949c06
diff --git a/framework-t/jni/onload.cpp b/framework-t/jni/onload.cpp
new file mode 100644
index 0000000..1fb42c6
--- /dev/null
+++ b/framework-t/jni/onload.cpp
@@ -0,0 +1,39 @@
+/*
+ * Copyright (C) 2022 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#define LOG_TAG "FrameworkConnectivityJNI"
+
+#include <log/log.h>
+#include <nativehelper/JNIHelp.h>
+
+namespace android {
+
+int register_android_net_TrafficStats(JNIEnv* env);
+
+extern "C" jint JNI_OnLoad(JavaVM* vm, void*) {
+    JNIEnv *env;
+    if (vm->GetEnv(reinterpret_cast<void**>(&env), JNI_VERSION_1_6) != JNI_OK) {
+        __android_log_print(ANDROID_LOG_ERROR, LOG_TAG, "ERROR: GetEnv failed");
+        return JNI_ERR;
+    }
+
+    if (register_android_net_TrafficStats(env) < 0) return JNI_ERR;
+
+    return JNI_VERSION_1_6;
+}
+
+};  // namespace android
+