[Audiosharing] UI refinement.

1. Add top summary for Audio sharing page.
2. Move Audio sharing entrance to the second place on Connection
   preferences page.
3. Make Audio sharing page searchable.
4. Add On/Off summary to Audio sharing preference on Connection
   preference page.

Test: atest
Bug: 305620450
Change-Id: I00019e53563afc0a539934fbdfa949c3401e78b9
diff --git a/res/xml/bluetooth_audio_sharing.xml b/res/xml/bluetooth_audio_sharing.xml
index d3aad22..ba3c083 100644
--- a/res/xml/bluetooth_audio_sharing.xml
+++ b/res/xml/bluetooth_audio_sharing.xml
@@ -19,6 +19,11 @@
     xmlns:settings="http://schemas.android.com/apk/res-auto"
     android:title="@string/audio_sharing_title">
 
+    <com.android.settingslib.widget.TopIntroPreference
+        android:key="audio_sharing_top_intro"
+        android:title="Let others listen to your media along with you using their own compatible headphones"
+        settings:searchable="false" />
+
     <PreferenceCategory
         android:key="audio_sharing_device_volume_group"
         android:title="Devices listening"