Use the vm tool

MicrodroidHostTestCases now uses the vm tool to create the VM. It no
longer directly interacts with crosvm and mk_cdisk.

The READMD.md file is rewritten to fully reflect the recent changes, and
also to add description about building an app for microdroid.

Bug: 185891097
Test: atest MicrodroidHostTestCases
Change-Id: I5fdc854390fd362ebead22a4a36af75c30500a81
diff --git a/microdroid/microdroid.json b/microdroid/microdroid.json
new file mode 100644
index 0000000..7dc4b6a
--- /dev/null
+++ b/microdroid/microdroid.json
@@ -0,0 +1,43 @@
+{
+  "bootloader": "/apex/com.android.virt/etc/microdroid_bootloader",
+  "disks": [
+    {
+      "partitions": [
+        {
+          "label": "boot_a",
+          "path": "/apex/com.android.virt/etc/fs/microdroid_boot-5.10.img"
+        },
+        {
+          "label": "vendor_boot_a",
+          "path": "/apex/com.android.virt/etc/fs/microdroid_vendor_boot-5.10.img"
+        },
+        {
+          "label": "vbmeta_a",
+          "path": "/apex/com.android.virt/etc/fs/microdroid_vbmeta.img"
+        },
+        {
+          "label": "vbmeta_system_a",
+          "path": "/apex/com.android.virt/etc/fs/microdroid_vbmeta_system.img"
+        },
+        {
+          "label": "super",
+          "path": "/apex/com.android.virt/etc/fs/microdroid_super.img"
+        }
+      ],
+      "writable": false
+    },
+    {
+      "partitions": [
+        {
+          "label": "uboot_env",
+          "path": "/apex/com.android.virt/etc/uboot_env.img"
+        }
+      ],
+      "writable": false
+    },
+    {
+      "image": "/data/local/tmp/virt/payload.img",
+      "writable": false
+    }
+  ]
+}