Move 'Audio Output' to Accessibility hearing device page

* Extract the common part into HearingAidHelper.
* Remove abstract getHearingDevice(). Change to get the hearing device when needed.
* Move several classes from Bluetooth into Accessibility

Bug: 281783079
Test: make RunSettingsRoboTests ROBOTEST_FILTER="(HearingDeviceAudioRoutingBasePreferenceControllerTest|AccessibilityHearingAidPreferenceControllerTest|HearingAidHelperTest|HearingAidAudioRoutingPreferenceControllerTest|HearingDeviceCallRoutingPreferenceControllerTest)"
Change-Id: I79049107409b7086c6dcc8d48a6323e171ed1535

src/com/android/settings/accessibility/HearingAidAudioRoutingPreferenceController.java

@@ -0,0 +1,38 @@
+/*
+ * Copyright (C) 2023 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 com.android.settings.accessibility;
+
+import android.content.Context;
+import android.util.FeatureFlagUtils;
+
+import com.android.settings.core.BasePreferenceController;
+
+/**
+ * The controller of the audio routing.
+ */
+public class HearingAidAudioRoutingPreferenceController extends BasePreferenceController {
+    public HearingAidAudioRoutingPreferenceController(Context context,
+            String preferenceKey) {
+        super(context, preferenceKey);
+    }
+
+    @Override
+    public int getAvailabilityStatus() {
+        return FeatureFlagUtils.isEnabled(mContext, FeatureFlagUtils.SETTINGS_AUDIO_ROUTING)
+                ? AVAILABLE : UNSUPPORTED_ON_DEVICE;
+    }
+}