Convert Tetheroffload HIDL to AIDL.

This patch converts Tetheroffload HIDL to AIDL and adds an empty
example implementation.
There are some changes in AIDL HAL:
1. Combine IOffloadConfig and IOffloadControl into IOffload
2. Use AIDL builtin errors exception code with message as return

Bug: b/205762647
Test: m android.hardware.tetheroffload-update-api
      m android.hardware.tetheroffload-V1-ndk
      m android.hardware.tetheroffload-service.example
      atest VtsHalTetheroffloadTargetTest
Change-Id: I9859ff3df608c058786b4e2b91cb6cd5f38e653a
diff --git a/tetheroffload/aidl/default/Android.bp b/tetheroffload/aidl/default/Android.bp
new file mode 100644
index 0000000..8f0739c
--- /dev/null
+++ b/tetheroffload/aidl/default/Android.bp
@@ -0,0 +1,36 @@
+// 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.
+
+package {
+    default_applicable_licenses: ["Android-Apache-2.0"],
+}
+
+cc_binary {
+    name: "android.hardware.tetheroffload-service.example",
+    relative_install_path: "hw",
+    init_rc: ["tetheroffload-example.rc"],
+    vintf_fragments: ["tetheroffload-example.xml"],
+    vendor: true,
+    shared_libs: [
+        "android.hardware.tetheroffload-V1-ndk",
+        "libbase",
+        "libbinder_ndk",
+        "libcutils",
+        "libutils",
+    ],
+    srcs: [
+        "main.cpp",
+        "Offload.cpp",
+    ],
+}