Add system feature for Companion Device Manager

Bug: 30932767
Test: Add just the feature gating first, ensure Context#getSystemSetrvice now
returns null.
Add feature in the configuration files, ensure companion device feature works again.
Change-Id: I4ad2d52f7877eae0e951f43ddbb23881d5de8d8b
diff --git a/services/java/com/android/server/SystemServer.java b/services/java/com/android/server/SystemServer.java
index 1a0aff7..8b5e24f 100644
--- a/services/java/com/android/server/SystemServer.java
+++ b/services/java/com/android/server/SystemServer.java
@@ -1376,9 +1376,11 @@
                 traceEnd();
             }
 
-            traceBeginAndSlog("StartCompanionDeviceManager");
-            mSystemServiceManager.startService(COMPANION_DEVICE_MANAGER_SERVICE_CLASS);
-            traceEnd();
+            if (mPackageManager.hasSystemFeature(PackageManager.FEATURE_COMPANION_DEVICE_SETUP)) {
+                traceBeginAndSlog("StartCompanionDeviceManager");
+                mSystemServiceManager.startService(COMPANION_DEVICE_MANAGER_SERVICE_CLASS);
+                traceEnd();
+            }
 
             traceBeginAndSlog("StartRestrictionManager");
             mSystemServiceManager.startService(RestrictionsManagerService.class);