authfs: implement fs-verity Merkle tree verification

The fs-verity verification is compatible to the original format in Linux
kernel. The current verification only verifies a chunk of content
against the Merkle tree, without any signature check yet.

Bug: 171310075
Test: atest authfs_host_test_src_lib
Test: stress test with lots of possible input sizes

Change-Id: Icf2194aa5ebf282936d7b304bcc956d39f500b1a
diff --git a/authfs/Android.bp b/authfs/Android.bp
index fe038cd..3c5849b 100644
--- a/authfs/Android.bp
+++ b/authfs/Android.bp
@@ -6,6 +6,7 @@
     ],
     edition: "2018",
     rustlibs: [
+        "libanyhow",
         "libauthfs_crypto_bindgen",
         "liblibc",
         "libthiserror",