compsvc: Notify VS when we're ready

Once our server socket is listening, notify virtualizationservice that
we're ready.

Modify clients to wait for ready instead of sleeping.

Bug: 186126194
Test: Manually run compos_key_cmd, compos_verify_key
Change-Id: Ibaff4bf22de9de2aa4faff9e81b24c779643b78c
diff --git a/virtualizationservice/aidl/Android.bp b/virtualizationservice/aidl/Android.bp
index 571cc5d..30a4b03 100644
--- a/virtualizationservice/aidl/Android.bp
+++ b/virtualizationservice/aidl/Android.bp
@@ -39,7 +39,10 @@
     backend: {
         rust: {
             enabled: true,
-            apex_available: ["com.android.virt"],
+            apex_available: [
+                "com.android.virt",
+                "com.android.compos",
+            ],
         },
     },
 }