Revert^2 "Migrate to avb_add_hash_footer"

Replace custom genrules with the new build rule for AVB signing images,
but this time the fake bootloader is changed from an empty file to the
avbpubkey so there doesn't need to be special handling for arm and x86
platforms.

This reverts commit 2ccf69446848202a016c6c95b33867ec70f776cb.

Test: Forrest built for aosp_x86-eng, which presubmit doesn't do
Change-Id: I6e37b41128fcfbb63a996ad564772458f6699f42
diff --git a/apex/Android.bp b/apex/Android.bp
index 4698088..923c378 100644
--- a/apex/Android.bp
+++ b/apex/Android.bp
@@ -3,12 +3,16 @@
 }
 
 microdroid_filesystem_images = [
-    "microdroid_super",
     "microdroid_boot",
+    "microdroid_bootconfig_app_debuggable",
+    "microdroid_bootconfig_full_debuggable",
+    "microdroid_bootconfig_normal",
     "microdroid_init_boot",
-    "microdroid_vendor_boot",
+    "microdroid_super",
+    "microdroid_uboot_env",
     "microdroid_vbmeta",
     "microdroid_vbmeta_bootconfig",
+    "microdroid_vendor_boot",
 ]
 
 apex {
@@ -60,12 +64,8 @@
     prebuilts: [
         "com.android.virt.init.rc",
         "microdroid.json",
-        "microdroid_uboot_env",
         "microdroid_bootloader",
         "microdroid_bootloader.avbpubkey",
-        "microdroid_bootconfig_normal",
-        "microdroid_bootconfig_app_debuggable",
-        "microdroid_bootconfig_full_debuggable",
     ],
     file_contexts: ":com.android.virt-file_contexts",
     canned_fs_config: "canned_fs_config",