Add a skeleton virtualizationmaintenance service

Create skeleton AIDL and service implementation, wire it all up, update
build files.

While I'm here, improve error handling, since it turns out that some
of the things we assumed can never happen actually can.

Bug: 294177871
Bug: 326125368
Test: atest MicrodroidTests
Change-Id: Ib792b8d523bcf4291fa56d117f1f10fed70498d6
diff --git a/virtualizationservice/Android.bp b/virtualizationservice/Android.bp
index e0bb97f..9c833e2 100644
--- a/virtualizationservice/Android.bp
+++ b/virtualizationservice/Android.bp
@@ -23,6 +23,7 @@
     rustlibs: [
         "android.hardware.security.rkp-V3-rust",
         "android.system.virtualizationcommon-rust",
+        "android.system.virtualizationmaintenance-rust",
         "android.system.virtualizationservice-rust",
         "android.system.virtualizationservice_internal-rust",
         "android.system.virtualmachineservice-rust",