Add persistent backing for encrypted storage in VM

Virtualization service will allow clients to pass the file that will
back the (encrypted) storage inside VM.

This patch:
1. Exposes (optional) encryptedStorageImage in VirtualMachineAppConfig.
2. Expose it as a block device to VM (by including it as partition in a
   writable disk).

Test: bin/vm run-app --storage -> inspect the block device in vm
Bug: 241543632
Change-Id: I9adbe832bda2c5f5a749d8614f056f51244ae52c
diff --git a/vm/src/main.rs b/vm/src/main.rs
index 21cc74b..3b887d3 100644
--- a/vm/src/main.rs
+++ b/vm/src/main.rs
@@ -58,6 +58,16 @@
         #[clap(short, long)]
         daemonize: bool,
 
+        /// Path to the file backing the storage.
+        /// Created if the option is used but the path does not exist in the device.
+        #[clap(long)]
+        storage: Option<PathBuf>,
+
+        /// Size of the storage. Used only if --storage is supplied but path does not exist
+        /// Default size is 10*1024*1024
+        #[clap(long)]
+        storage_size: Option<u64>,
+
         /// Path to file for VM console output.
         #[clap(long)]
         console: Option<PathBuf>,
@@ -188,6 +198,8 @@
             apk,
             idsig,
             instance,
+            storage,
+            storage_size,
             config_path,
             daemonize,
             console,
@@ -205,6 +217,8 @@
             &apk,
             &idsig,
             &instance,
+            storage.as_deref(),
+            storage_size,
             config_path.as_deref().unwrap_or(""),
             daemonize,
             console.as_deref(),