authfs: Remote file editor over binder

The remote editor allows to read/write from/to a remote file. This
change:
 - Adds new binder API `writeFile`.
 - Update fd_server to serve a read/writable fd. Read operation is done
   through the existing read API when applicable.
 - Adds `RemoteFileEditor` as a binder client for both read and write.

Bug: 171279640
Test: adb shell exec 9<>/data/local/tmp/output fd_server --rw-fds 9
Test: with changes in fusefs.rs, saw file changed correctly (md5sum)

Change-Id: I78ef198ee8a3a0f2d99717dc0c00fccde757f3de
diff --git a/authfs/fd_server/Android.bp b/authfs/fd_server/Android.bp
index 6f010ce..9c810a8 100644
--- a/authfs/fd_server/Android.bp
+++ b/authfs/fd_server/Android.bp
@@ -7,6 +7,7 @@
     srcs: ["src/main.rs"],
     rustlibs: [
         "authfs_aidl_interface-rust",
+        "libandroid_logger",
         "libanyhow",
         "libbinder_rs",
         "libclap",