remove support of multi-file partition

This is a non-trivial revert of 9713bd4664034f4a0c2f8ffbb289bd19481d4800
and 1fee0d8da6bb440127861e278a7dad09b7f506fd.

Bug: n/a
Test: atest MicrodroidHostTestCases
Change-Id: I2cd549ddbdb2c28c251697789c101d0af1885fdf
diff --git a/microdroid/microdroid.json b/microdroid/microdroid.json
index da82289..1337edf 100644
--- a/microdroid/microdroid.json
+++ b/microdroid/microdroid.json
@@ -5,23 +5,23 @@
       "partitions": [
         {
           "label": "boot_a",
-          "paths": ["/apex/com.android.virt/etc/fs/microdroid_boot-5.10.img"]
+          "path": "/apex/com.android.virt/etc/fs/microdroid_boot-5.10.img"
         },
         {
           "label": "vendor_boot_a",
-          "paths": ["/apex/com.android.virt/etc/fs/microdroid_vendor_boot-5.10.img"]
+          "path": "/apex/com.android.virt/etc/fs/microdroid_vendor_boot-5.10.img"
         },
         {
           "label": "vbmeta_a",
-          "paths": ["/apex/com.android.virt/etc/fs/microdroid_vbmeta.img"]
+          "path": "/apex/com.android.virt/etc/fs/microdroid_vbmeta.img"
         },
         {
           "label": "vbmeta_system_a",
-          "paths": ["/apex/com.android.virt/etc/fs/microdroid_vbmeta_system.img"]
+          "path": "/apex/com.android.virt/etc/fs/microdroid_vbmeta_system.img"
         },
         {
           "label": "super",
-          "paths": ["/apex/com.android.virt/etc/fs/microdroid_super.img"]
+          "path": "/apex/com.android.virt/etc/fs/microdroid_super.img"
         }
       ],
       "writable": false
@@ -30,7 +30,7 @@
       "partitions": [
         {
           "label": "uboot_env",
-          "paths": ["/apex/com.android.virt/etc/uboot_env.img"],
+          "path": "/apex/com.android.virt/etc/uboot_env.img",
           "writable": false
         }
       ],