Add auto_memory_balloon in vm_config.json

Bug: 363985291
Test: turn on auto_memory_balloon, and check balloon option in crosvm
Test: adb shell am send-trim-memory com.android.virtualization.terminal
  RUNNING_MODERATE
Change-Id: I3a1801331bc60d00a7d1aa8bdc46bb287298f972
diff --git a/android/TerminalApp/java/com/android/virtualization/terminal/ConfigJson.java b/android/TerminalApp/java/com/android/virtualization/terminal/ConfigJson.java
index b79e346..a0fca82 100644
--- a/android/TerminalApp/java/com/android/virtualization/terminal/ConfigJson.java
+++ b/android/TerminalApp/java/com/android/virtualization/terminal/ConfigJson.java
@@ -76,6 +76,7 @@
     private SharedPathJson[] sharedPath;
     private DisplayJson display;
     private GpuJson gpu;
+    private boolean auto_memory_balloon;
 
     /** Parses JSON file at jsonPath */
     static ConfigJson from(Context context, Path jsonPath) {
@@ -145,7 +146,8 @@
                 .setBootloaderPath(bootloader)
                 .setKernelPath(kernel)
                 .setInitrdPath(initrd)
-                .useNetwork(network);
+                .useNetwork(network)
+                .useAutoMemoryBalloon(auto_memory_balloon);
 
         if (input != null) {
             builder.useTouch(input.touchscreen)