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/apex/Android.bp b/apex/Android.bp
index 32f88e1..ef7677b 100644
--- a/apex/Android.bp
+++ b/apex/Android.bp
@@ -91,6 +91,7 @@
     ],
     prebuilts: [
         "com.android.virt.init.rc",
+        "features_com.android.virt.xml",
         "microdroid_initrd_app_debuggable",
         "microdroid_initrd_full_debuggable",
         "microdroid_initrd_normal",