WebAPI: Add metadata in /app/getDirectoryContent response

## Description

Send file/folder metadata instead of just the name of a filesystem entry.
Currently the endpoint only sends a list of string, containing the path of each entry, without specifying its type (file or folder).
The optional `withMetadata` flag has been added to provide metadata and to prevent breaking changes with older versions.
If `true`, JSON response will be an array of objects instead of an array of strings.

This object contains:
- `name`: the name of the file system entry (without path)
- `type`: Whether the file system entry is a "file" or a "dir"
- `creation_date`: file system entry's creation date
- `last_access_date`: file system entry's last access date
- `last_modification_date`: file system entry's last modification date

If the entry is a file, a `size` field is present with the file size in bytes.

## Objective

Build a server file browser inside WebUIs, feature is currently being developed for VueTorrent.
It will include file metadata, filtering and sorting on the different fields.

PR #22813.

src/webui/webapplication.h

@@ -53,7 +53,7 @@
 #include "base/utils/version.h"
 #include "api/isessionmanager.h"
 
-inline const Utils::Version<3, 2> API_VERSION {2, 11, 7};
+inline const Utils::Version<3, 2> API_VERSION {2, 11, 8};
 
 class APIController;
 class AuthController;