Add config for call captioning

Add a definition for a boolean config value that will be used by the
system captioning service to check whether calls captioning should be
enabled on the device.

Bug: 136282740, 208740916.
Test: Manually.
Change-Id: I6cf894f7dcc7d650ddf4a89e0d356b1da83bf67e

core/api/system-current.txt

@@ -353,6 +353,7 @@ package android {
     field public static final int config_showDefaultAssistant = 17891329; // 0x1110001
     field public static final int config_showDefaultEmergency = 17891330; // 0x1110002
     field public static final int config_showDefaultHome = 17891331; // 0x1110003
+    field public static final int config_systemCaptionsServiceCallsEnabled;
   }
 
   public static final class R.color {

core/res/res/values/config.xml

@@ -4008,6 +4008,11 @@
     -->
     <string name="config_defaultSystemCaptionsManagerService" translatable="false"></string>
 
+    <!-- Indicates whether the system wide captions service should also support
+         call captioning.
+    -->
+    <bool name="config_systemCaptionsServiceCallsEnabled" translatable="false"></bool>
+
     <!-- The package name for the incident report approver app.
         This app is usually PermissionController or an app that replaces it.  When
         a bugreport or incident report with EXPLICT-level sharing flags is going to be

core/res/res/values/public.xml

@@ -3362,6 +3362,8 @@
   </staging-public-group>
 
   <staging-public-group type="bool" first-id="0x01cf0000">
+    <!-- @hide @SystemApi -->
+    <public name="config_systemCaptionsServiceCallsEnabled" />
   </staging-public-group>
 
   <staging-public-group type="fraction" first-id="0x01ce0000">