Update littlefs from 2.4.0 -> 2.9.3 (#2777)

This PR updates the [Sming-LittleFS](https://github.com/mikee47/Sming-LittleFS) library, which implements IFS for the [littlefs](https://github.com/littlefs-project/littlefs) file system.

The library still uses a fork of littlefs because it adds attribute enumeration support - see upstream [PR request](littlefs-project/littlefs#636). This has now been rebased on version 2.9.3 - see [releases](https://github.com/littlefs-project/littlefs/releases) for details of all the changes. Here's a (non-exhaustive) summary:

- Improved RAM usage
- Improved performance
- v2.5.0 removed all recursion
- v2.6.0 bump the on-disk minor version of littlefs from lfs2.0 -> lfs2.1. "This change is backwards-compatible, but after the first write with the new version, the image on disk will no longer be mountable by older versions of littlefs."
- v2.7.0 Add `lfs_fs_stat` as an analog for the POSIX stavfs. This isn't currently used by Sming-LittleFS.
- v2.9.0 `rename` now returns LFS_ERR_NOTDIR if the source is a regular file and the destination is a directory. This better aligns with POSIX.

There are no functional changes to the library, but the samples have been simplified. An additional sample has been added to assess wear levelling behaviour (as a result of discussion #2771).