Add maintenance as a lazy service

We need to advertise it as a lazy service to allow VS to be started
when it is needed.

To avoid having to have 4 variants of the .rc file, switch from
picking one to constructing it from fragments.

Bug: 294177871
Test: Builds, final .rc is correct
Change-Id: I10faf32249e41cab21a602f94231786f95e20d3d
diff --git a/apex/virtualizationservice.rc.llpvm b/apex/virtualizationservice.rc.llpvm
new file mode 100644
index 0000000..916d508
--- /dev/null
+++ b/apex/virtualizationservice.rc.llpvm
@@ -0,0 +1 @@
+    interface aidl android.system.virtualizationmaintenance