Add support for MapServer OGC API - Features output

[gfenoy]

Despite the fact that the MapServer support, that we implemented some years ago, has been integrated within the current implementation of the OGC API - Processes, the output does not use the OGC API - Features capability that is now offered by MapServer as per the following RFC.

In consequence, we need to make the appropriate updates to the current implementation to support the OGC API - Features to be supported as an output format.

I think we can keep the same way of linking the useMapserver within the metadata file / database entries to the output formats. Obviously, this time we may use the application/json mimeType metadata information to detect that the OGC API - Features is required and we can keep the same behavior for text/xml which will output a WFS GetFeature request, and all the rest say unchanged.