misc: vmm: drop extern crate, use modern rust

This commit is part of a series of similar commits.

Signed-off-by: Philipp Schuster <philipp.schuster@cyberus-technology.de>
On-behalf-of: SAP philipp.schuster@sap.com

vmm/src/memory_manager.rs

@@ -25,6 +25,9 @@ use devices::ioapic;
 #[cfg(target_arch = "aarch64")]
 use hypervisor::HypervisorVmError;
 use libc::_SC_NPROCESSORS_ONLN;
+#[cfg(all(target_arch = "x86_64", feature = "guest_debug"))]
+use log::debug;
+use log::{error, info, warn};
 use serde::{Deserialize, Serialize};
 use thiserror::Error;
 use tracer::trace_scoped;