Revert^2 "Boot VM without bootloader - using init ramdisk"

Remove ABL from the boot flow of VMs. Virtualization service uses
microdroid.json to construct the appropriate vm_config.

Partitions:
1. Boot related partitions (boot/init_boot/vendor_boot) are no more
   required. kernel & init ramdisk is directly passed via crosvm command
   line.
2. uboot_env is obsolete without ABL
3. bootconfig partition is no more required because we are attaching the
   bootconfigs to initrd image.

This reverts commit 0f71596bd5333f08d07ed33dbb5425390dd8aa79

Bug: 240235424
Test: atest MicrodroidTestCase
Change-Id: I1b4c3ec792db9898093c4ccd3c037657c50a934f
diff --git a/apex/Android.bp b/apex/Android.bp
index fade6c5..52f4384 100644
--- a/apex/Android.bp
+++ b/apex/Android.bp
@@ -69,6 +69,7 @@
         "microdroid.json",
         "microdroid_bootloader",
         "microdroid_bootloader.avbpubkey",
+        "microdroid_kernel",
     ],
     file_contexts: ":com.android.virt-file_contexts",
     canned_fs_config: "canned_fs_config",