SensitivePhoneNumbers: Convert to singleton class

* Now that there are more users than just call log, it is better to parse
  the XML-file just once
* Keep an instance around for the various users of this class

Change-Id: Iff1510dc40d68a211a6a1c5f19e4ca9ac64c3fcd

sdk/src/java/org/lineageos/internal/phone/SensitivePhoneNumbers.java

@@ -50,12 +50,21 @@ public class SensitivePhoneNumbers {
     public static final String SENSIBLE_PHONENUMBERS_FILE_PATH = "etc/sensitive_pn.xml";
     private static final String ns = null;
 
+    private static SensitivePhoneNumbers sInstance = null;
+
     private HashMap<String, ArrayList<String>> mSensitiveNumbersMap = new HashMap<>();
 
-    public SensitivePhoneNumbers() {
+    private SensitivePhoneNumbers() {
         loadSensiblePhoneNumbers();
     }
 
+    public static SensitivePhoneNumbers getInstance() {
+        if (sInstance == null) {
+            sInstance = new SensitivePhoneNumbers();
+        }
+        return sInstance;
+    }
+
     private void loadSensiblePhoneNumbers() {
         FileReader sensiblePNReader;