aconfig: Add resetAll method to test mode FeatureFlagsImpl

Add resetAll method to test mode FeatureFlagsImpl. This method
is used to reset all the flags values to null. It provides convenient
way to the test tools to reset the flags values.

Bug: 280833463
Test: atest aconfig.test
Change-Id: I4bf1d3ba69ee106ef8d0c1cc62c00bbeca1b72aa
diff --git a/tools/aconfig/templates/FeatureFlagsImpl.java.template b/tools/aconfig/templates/FeatureFlagsImpl.java.template
index f5edd1b..082d476 100644
--- a/tools/aconfig/templates/FeatureFlagsImpl.java.template
+++ b/tools/aconfig/templates/FeatureFlagsImpl.java.template
@@ -3,6 +3,7 @@
 import static java.util.stream.Collectors.toMap;
 
 import java.util.HashMap;
+import java.util.Map;
 import java.util.stream.Stream;
 {{ else}}
 {{ if is_read_write- }}
@@ -36,6 +37,12 @@
         this.mFlagMap.put(flagName, value);
     }
 
+    public void resetAll() \{
+        for (Map.Entry entry : mFlagMap.entrySet()) \{
+            entry.setValue(null);
+        }
+    }
+
     private boolean getFlag(String flagName) \{
         Boolean value = this.mFlagMap.get(flagName);
         if (value == null) \{