vold: allow specifying HEH filenames encryption

Make the vold changes needed to support specifying aes-256-heh filenames
encryption.  The previous mode, aes-256-cts, remains supported as well.

The file /data/unencrypted/mode is updated to have the syntax
contents_encryption_mode[:filenames_encryption_mode] instead of just
contents_encryption_mode.  This is consistent with the new fstab syntax.

Bug: 34712722
Change-Id: Ibc236d0ec4fdeda4e4e301f45fb996317692cfa3
diff --git a/cryptfs.c b/cryptfs.c
index e2606ec..41be686 100644
--- a/cryptfs.c
+++ b/cryptfs.c
@@ -3879,8 +3879,9 @@
                               ftr);
 }
 
-const char* cryptfs_get_file_encryption_mode()
+void cryptfs_get_file_encryption_modes(const char **contents_mode_ret,
+                                       const char **filenames_mode_ret)
 {
     struct fstab_rec* rec = fs_mgr_get_entry_for_mount_point(fstab, DATA_MNT_POINT);
-    return fs_mgr_get_file_encryption_mode(rec);
+    fs_mgr_get_file_encryption_modes(rec, contents_mode_ret, filenames_mode_ret);
 }