Make exporting tombstone (out of VM) configurable

VM owner must specify export_tombstones value in assets/vm_config in
payload apk to enable/disable exporting the tombstones out of VM. This
is also dm-verity protected so only the owner of the VM can make the
change.  There is no default value for this for now. Virtualization
service will fail at load_config() throw binder_exception to client.

Test: atest . (all tests in /packages/modules/Virtualization)
Bug: 227443903

Change-Id: I82325a9ffc57d4d4825d51d9d41ebb767e6c1f6f
diff --git a/microdroid/payload/config/src/lib.rs b/microdroid/payload/config/src/lib.rs
index 67e8feb..b82544f 100644
--- a/microdroid/payload/config/src/lib.rs
+++ b/microdroid/payload/config/src/lib.rs
@@ -38,6 +38,10 @@
     /// Tells VirtualizationService to use staged APEXes if possible
     #[serde(default)]
     pub prefer_staged: bool,
+
+    /// Whether to export the tomsbtones (VM crashes) out of VM to host
+    /// This does not have a default & the value is expected to be in json for deserialization
+    pub export_tombstones: bool,
 }
 
 /// OS config