Microdroid activates host APEXes

Host apexes are passed to microdroid via the payload composite image.
The payload composite image can be created by either
mk_payload_signature/mk_cdisk or mk_payload.

For now, microdroid expects two APEXes from the host:
- com.android.adbd
- com.android.sdkext

The exact set of host apexes for microdroid is TBD. The current set is
only for demonstration.

Bug: 181093750
Test: MicrodroidTestCase
Change-Id: I7fe33fe03ac94799a4e109b83286bfb39e44b882
diff --git a/microdroid/init.rc b/microdroid/init.rc
index 56b0065..61f9ae5 100644
--- a/microdroid/init.rc
+++ b/microdroid/init.rc
@@ -105,6 +105,8 @@
 
     perform_apex_config
 
+    exec_start derive_sdk
+
     start adbd
 
 service ueventd /system/bin/ueventd
@@ -122,13 +124,6 @@
     seclabel u:r:shell:s0
     setenv HOSTNAME console
 
-# TODO(b/181093750): remove these after adding apex support
-service adbd /system/bin/adbd --root_seclabel=u:r:su:s0
-    class core
-    socket adbd seqpacket 660 system system
-    disabled
-    seclabel u:r:adbd:s0
-
 on fs
     write /dev/event-log-tags "# content owned by logd
 "