Fix Bluetooth enable dialog to match Android style guide.

When an app requests to enable Bluetooth and/or Bluetooth discovery,
we show a dialog for user confirmation. Remove the dialog title,
update the message text and button labels to be more descriptive,
and use the standard dialog layout instead of a custom layout.

Also fixes the button layout on the Bluetooth permission test app so
that the "Discoverable" button doesn't wrap to two lines.

Bug: 6001468
Change-Id: I731e2f31b4c822395fc3f83584a092550d9ae7d3

res/layout/bluetooth_discoverable.xml

@@ -1,33 +0,0 @@
-<?xml version="1.0" encoding="utf-8"?>
-<!--
-/*
-** Copyright 2009, 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.
-*/
--->
-
-<ScrollView
-    xmlns:android="http://schemas.android.com/apk/res/android"
-    android:layout_height="match_parent"
-    android:layout_width="match_parent">
-
-    <TextView
-        android:id="@+id/message"
-        android:layout_width="match_parent"
-        android:layout_height="wrap_content"
-        android:paddingStart="20dip"
-        android:paddingEnd="20dip"
-        android:gravity="center_horizontal"
-        android:textAppearance="?android:attr/textAppearanceMedium" />
-</ScrollView>