microdroid: create payload disk image with system apexes

Virtualizationservice creates a pyload disk image only for "microdroid"
and it adds necessary system apexes automatically.

Removed those apexes from vm_config.json files in testapk and compos
apk.

Bug: 190503456
Bug: 192200378
Test: adb root && adb shell setenforce 0
Test: adb shell /apex/com.android.virt/bin/vm run-app \
  /apex/com.android.compos/app/CompOSPayloadApp/CompOSPayloadApp.apk \
  /apex/com.android.compos/etc/CompOSPayloadApp.apk.idsig \
  assets/vm_config.json
Change-Id: I7d472ea0876f2571ca6767e2ba0b5773a951368b
diff --git a/compos/apex/Android.bp b/compos/apex/Android.bp
index 9942e09..1fffa2e 100644
--- a/compos/apex/Android.bp
+++ b/compos/apex/Android.bp
@@ -48,6 +48,6 @@
     ],
 
     prebuilts: [
-        "compos_payload_config",
+        "CompOSPayloadApp.apk.idsig",
     ],
 }