Migrate to avb_add_hash_footer

Replace custom genrules with the new build rule for AVB signing images.

Test: build and microdroid tests
Bug: 234564414
Bug: 185115783
Change-Id: I7886ff2695c6892de4be60db47c652b100515787
diff --git a/virtualizationservice/src/payload.rs b/virtualizationservice/src/payload.rs
index 7b8cb7f..8378df3 100644
--- a/virtualizationservice/src/payload.rs
+++ b/virtualizationservice/src/payload.rs
@@ -365,7 +365,7 @@
         )?),
         writable: false,
     });
-    let bootconfig_image = "/apex/com.android.virt/etc/microdroid_bootconfig.".to_owned()
+    let bootconfig_image = "/apex/com.android.virt/etc/fs/microdroid_bootconfig.".to_owned()
         + match config.debugLevel {
             DebugLevel::NONE => "normal",
             DebugLevel::APP_ONLY => "app_debuggable",