Revert "vm tool: rename --gki arg to more generic --os one"

Revert submission 3323102

Reason for revert: DroidMonitor: Potential culprit for http://b/376483022 - verifying through ABTD before revert submission. This is part of the standard investigation process, and does not mean your CL will be reverted.

Reverted changes: /q/submissionid:3323102

Change-Id: Id2923b891929dd695821da09a116a95d16ef8372
diff --git a/android/vm/src/run.rs b/android/vm/src/run.rs
index b07a472..0e1f4cc 100644
--- a/android/vm/src/run.rs
+++ b/android/vm/src/run.rs
@@ -140,7 +140,11 @@
         bail!("Either --config-path or --payload-binary-name must be defined")
     };
 
-    let os_name = if let Some(ref os) = config.microdroid.os { os } else { "microdroid" };
+    let os_name = if let Some(ver) = config.microdroid.gki() {
+        format!("microdroid_gki-{ver}")
+    } else {
+        "microdroid".to_owned()
+    };
 
     let payload_config_str = format!("{:?}!{:?}", config.apk, payload);
 
@@ -188,7 +192,7 @@
         memoryMib: config.common.mem.unwrap_or(0) as i32, // 0 means use the VM default
         cpuTopology: config.common.cpu_topology,
         customConfig: Some(custom_config),
-        osName: os_name.to_string(),
+        osName: os_name,
         hugePages: config.common.hugepages,
         boostUclamp: config.common.boost_uclamp,
     });