Support the rich content for accessibility service (1/n)

Goal: 1. let third party developer can use html text that include from their local image file and
         animated image instead of only plain text to rich their content.
      2. Avoid malicious links made by third party developer

Action: 1. Add html, static text, and animated image preferences.
        2. Add android:AnimatedImageDrawable, and android:htmlDescription attributes.
        3. Fine-tune interface and integration
        4. Add custom tag filter

Bug: 136292241
Test: Maunal & make RunSettingsRoboTests
Change-Id: I82cd5319efb7faa1ff7e8354a279828fce5135b8

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

@@ -0,0 +1,42 @@
+/*
+ * Copyright (C) 2019 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 androidx.preference.Preference;
+import androidx.preference.PreferenceViewHolder;
+
+import com.android.settings.R;
+
+/**
+ * A custom {@link android.widget.TextView} preference that removes the title and summary
+ * restriction from platform {@link Preference} implementation and the icon location is kept as
+ * gravity top instead of center.
+ */
+public class StaticTextPreference extends Preference {
+
+    StaticTextPreference(Context context) {
+        super(context);
+        setLayoutResource(R.layout.preference_static_text);
+    }
+
+    @Override
+    public void onBindViewHolder(PreferenceViewHolder holder) {
+        super.onBindViewHolder(holder);
+    }
+}