Refactor webrtc audio management

Attempts to:

1) Successfully play ringtone through speaker instead of earpiece
   when possible.

2) Manage bluetooth headset connectivity as well as possible

3) Eliminate notification sounds while in-call when possible

4) Make sure audio is correctly setup when receiving calls

Fixes #6271
Fixes #6248
Fixes #6238
Fixes #6184
Fixes #6169

// FREEBIE

res/drawable/webrtc_audio_button.xml

@@ -1,47 +0,0 @@
-<?xml version="1.0" encoding="utf-8"?>
-<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
-    <item android:id="@+id/compoundBackgroundItem" android:drawable="@drawable/webrtc_control_background"/>
-
-    <item android:id="@+id/moreIndicatorItem"
-          android:top="5dp"
-          android:left="5dp"
-          android:right="5dp"
-          android:bottom="5dp">
-        <bitmap android:src="@drawable/redphone_ic_more_indicator_holo_dark"
-                android:gravity="bottom|right" />
-    </item>
-
-    <item android:id="@+id/bluetoothItem"
-          android:top="5dp"
-          android:left="5dp"
-          android:right="5dp"
-          android:bottom="5dp">
-        <bitmap android:src="@drawable/ic_phone_bluetooth_speaker_white_24dp"
-                android:gravity="center" />
-    </item>
-
-    <!-- Handset earpiece is active -->
-    <item android:id="@+id/handsetItem" android:top="5dp"
-          android:left="5dp"
-          android:right="5dp"
-          android:bottom="5dp">
-        <bitmap android:src="@drawable/ic_phone_in_talk_white_24dp"
-                android:gravity="center" />
-    </item>
-
-    <!-- Speakerphone icon showing 'speaker on' state -->
-    <item android:id="@+id/speakerphoneOnItem" android:top="5dp"
-          android:left="5dp"
-          android:right="5dp"
-          android:bottom="5dp">
-        <bitmap android:src="@drawable/ic_volume_up_white_24dp"
-                android:gravity="center" />
-    </item>
-
-    <!--&lt;!&ndash; Speakerphone icon showing 'speaker off' state &ndash;&gt;-->
-    <!--<item android:id="@+id/speakerphoneOffItem">-->
-        <!--<bitmap android:src="@drawable/ic_volume_mute_white_24dp"-->
-                <!--android:gravity="center" />-->
-    <!--</item>-->
-
-</layer-list>

res/drawable/webrtc_bluetooth_button.xml

@@ -0,0 +1,9 @@
+<?xml version="1.0" encoding="utf-8"?>
+<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
+    <item android:drawable="@drawable/webrtc_control_background"/>
+    <item android:top="5dp"
+          android:left="5dp"
+          android:right="5dp"
+          android:bottom="5dp"
+          android:drawable="@drawable/ic_bluetooth_white_24dp"/>
+</layer-list>

res/drawable/webrtc_speaker_button.xml

@@ -0,0 +1,9 @@
+<?xml version="1.0" encoding="utf-8"?>
+<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
+    <item android:drawable="@drawable/webrtc_control_background"/>
+    <item android:top="5dp"
+          android:left="5dp"
+          android:right="5dp"
+          android:bottom="5dp"
+          android:drawable="@drawable/ic_volume_up_white_24dp"/>
+</layer-list>

res/layout/webrtc_call_controls.xml

@@ -7,12 +7,18 @@
               android:orientation="horizontal"
               tools:background="@color/textsecure_primary">
 
-        <ToggleButton android:id="@+id/audioButton"
+        <ToggleButton android:id="@+id/speakerButton"
                       style="@style/WebRtcCallCompoundButton"
-                      android:background="@drawable/webrtc_audio_button"
+                      android:background="@drawable/webrtc_speaker_button"
                       tools:checked="true"
                       android:layout_marginRight="15dp"/>
 
+        <ToggleButton android:id="@+id/bluetoothButton"
+                      style="@style/WebRtcCallCompoundButton"
+                      android:background="@drawable/webrtc_bluetooth_button"
+                      tools:checked="true"
+                      android:layout_marginRight="15dp"
+                      android:visibility="gone"/>
 
         <ToggleButton android:id="@+id/muteButton"
                       style="@style/WebRtcCallCompoundButton"

res/layout/webrtc_call_screen.xml

@@ -176,7 +176,6 @@
                     android:layout_width="match_parent"
                     android:layout_height="wrap_content"
                     android:background="@color/textsecure_primary"
-
                     android:paddingLeft="24dp"
                     android:paddingRight="24dp"
                     android:paddingTop="16dp"