Add `vm console` command to connect to serial console

`vm console` automatically connects to the first available VM.
`vm console CID` connects to the specified VM.

* Must also pass the `-t` flag to adb-shell to ensure adbd allocates a
  tty.

Bug: 335362012
Test: Launch FC and connect to serial console
  adb shell -t /apex/com.android.virt/bin/vm console
Change-Id: If5f1537d8994593ab7fa026bf98986c6a8c83cb5
diff --git a/virtualizationmanager/src/crosvm.rs b/virtualizationmanager/src/crosvm.rs
index 7769f61..637fe31 100644
--- a/virtualizationmanager/src/crosvm.rs
+++ b/virtualizationmanager/src/crosvm.rs
@@ -283,7 +283,7 @@
 #[derive(Debug)]
 pub struct VmContext {
     #[allow(dead_code)] // Keeps the global context alive
-    global_context: Strong<dyn IGlobalVmContext>,
+    pub(crate) global_context: Strong<dyn IGlobalVmContext>,
     #[allow(dead_code)] // Keeps the server alive
     vm_server: RpcServer,
 }
@@ -302,7 +302,7 @@
     pub vm_state: Mutex<VmState>,
     /// Global resources allocated for this VM.
     #[allow(dead_code)] // Keeps the context alive
-    vm_context: VmContext,
+    pub(crate) vm_context: VmContext,
     /// The CID assigned to the VM for vsock communication.
     pub cid: Cid,
     /// Path to crosvm control socket