authfs: Reorganize modules & rename flags/classes/vars

This change adjusts the module/directory layout to make it easier to
reason.

 - File "transports" are now under file/. Common traits are defined in
   file.rs.

 - All fs-verity related modules are now under fsverity/. This includes
   VerifiedFileReader, which implements traits in the file module to
   provide transparent verification.

 - Rename structs for better consistency.  Drop "Chunked" for
   simplicity.

    ChunkedFileReader          ->  LocalFileReader
    RemoteChunkedFileReader    ->  RemoteFileReader
    FsverityChunkedFileReader  ->  VerifiedFileReader

 - Move and rename get_local_service from remote_file.rs to file.rs.

Also, rename command line flags and related class/field names in main.rs
so that later the name of new read-writable file can fit in more consistently.

New layours:
  src/
  |-- auth.rs
  |-- common.rs
  |-- crypto.hpp
  |-- crypto.rs
  |-- file.rs
  |-- file
  |   |-- local_file.rs
  |   `-- remote_file.rs
  |-- fsverity.rs
  |-- fsverity
  |   |-- builder.rs
  |   |-- common.rs
  |   |-- sys.rs
  |   |-- verifier.rs
  |   `-- editor.rs
  |-- fusefs.rs
  `-- main.rs

Bug: 171279640
Test: atest

Change-Id: Ib257a37df89c6b813f4d97978678db3483d28b57
diff --git a/authfs/tools/device-test.sh b/authfs/tools/device-test.sh
index 5cf5f10..e85ad17 100755
--- a/authfs/tools/device-test.sh
+++ b/authfs/tools/device-test.sh
@@ -33,13 +33,13 @@
 # certificate.
 authfs \
   ${MOUNTPOINT} \
-  --local-verified-file 2:input.4m:input.4m.merkle_dump:input.4m.fsv_sig:/dev/null \
-  --local-verified-file 3:input.4k1:input.4k1.merkle_dump:input.4k1.fsv_sig:/dev/null \
-  --local-verified-file 4:input.4k:input.4k.merkle_dump:input.4k.fsv_sig:/dev/null \
-  --local-unverified-file 5:/system/bin/sh \
-  --remote-unverified-file 6:9:${size} \
-  --remote-verified-file 7:8:${size2}:/dev/null \
-  --remote-verified-file 8:5:${size2}:/dev/null \
+  --local-ro-file 2:input.4m:input.4m.merkle_dump:input.4m.fsv_sig:/dev/null \
+  --local-ro-file 3:input.4k1:input.4k1.merkle_dump:input.4k1.fsv_sig:/dev/null \
+  --local-ro-file 4:input.4k:input.4k.merkle_dump:input.4k.fsv_sig:/dev/null \
+  --local-ro-file-unverified 5:/system/bin/sh \
+  --remote-ro-file-unverified 6:9:${size} \
+  --remote-ro-file 7:8:${size2}:/dev/null \
+  --remote-ro-file 8:5:${size2}:/dev/null \
   &
 sleep 0.1