Refactor vm_config.json parsing routine

The routine is separate into a dedicated class. The parsing is now done
structurally using Gson.

Bug: N/A
Test: run Ferrochrome

Change-Id: I25cac5e8a7a12a7a0e6493a9362a239e43a00274
diff --git a/android/VmLauncherApp/Android.bp b/android/VmLauncherApp/Android.bp
index 7103d53..7dd2473 100644
--- a/android/VmLauncherApp/Android.bp
+++ b/android/VmLauncherApp/Android.bp
@@ -11,6 +11,7 @@
         "android.system.virtualizationservice_internal-java",
         // TODO(b/331708504): will be removed when AVF framework handles surface
         "libcrosvm_android_display_service-java",
+        "gson",
     ],
     libs: [
         "framework-virtualization.impl",
@@ -22,7 +23,7 @@
         "com.android.virt",
     ],
     optimize: {
-        optimize: true,
+        proguard_flags_files: ["proguard.flags"],
         shrink_resources: true,
     },
 }