Add android.software.virtualization_framework system feature

This feature can be used by applications to determine whether device
supports Android Virtualization Framework.

The feature is defined in the features_com.android.virt.xml that is
bundled inside the com.android.virt APEX.

Bug: 243512044
Test: install virt APEX
Test: adb shell pm list features
Change-Id: I0f1143dff158c6f0a266315a9f3b7c1c50e8a051
diff --git a/demo/AndroidManifest.xml b/demo/AndroidManifest.xml
index 6669adb..8fde69e 100644
--- a/demo/AndroidManifest.xml
+++ b/demo/AndroidManifest.xml
@@ -4,6 +4,7 @@
 
     <uses-permission android:name="android.permission.MANAGE_VIRTUAL_MACHINE" />
     <uses-sdk android:minSdkVersion="33" android:targetSdkVersion="33"/>
+    <uses-feature android:name="android.software.virtualization_framework" android:required="true" />
     <application
         android:label="MicrodroidDemo"
         android:theme="@style/Theme.MicrodroidDemo"