Adds default (mock) Context Hub HAL 1.2 impl

Also refactors common code.

Bug: 166845383
Test: Compile only (VTS test coming up in future CL)
Change-Id: Iae6cf09e2fffb854af61c29e6004ceb062a892b3
diff --git a/contexthub/1.2/default/Contexthub.cpp b/contexthub/1.2/default/Contexthub.cpp
new file mode 100644
index 0000000..d7ac7bf
--- /dev/null
+++ b/contexthub/1.2/default/Contexthub.cpp
@@ -0,0 +1,38 @@
+/*
+ * Copyright (C) 2020 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.
+ */
+#include "Contexthub.h"
+
+#include <vector>
+
+namespace android {
+namespace hardware {
+namespace contexthub {
+namespace V1_2 {
+namespace implementation {
+
+Return<void> Contexthub::onSettingChanged(SettingV1_1 /*setting*/, SettingValue /*newValue*/) {
+    return Void();
+}
+
+Return<void> Contexthub::onSettingChanged_1_2(Setting /*setting*/, SettingValue /*newValue*/) {
+    return Void();
+}
+
+}  // namespace implementation
+}  // namespace V1_2
+}  // namespace contexthub
+}  // namespace hardware
+}  // namespace android