Add POST data for orderBy and orderDir in the filter processing.

[zonky2]

Add POST data for orderBy and orderDir in the filter processing.

Add POST data to slug parameter here https://github.com/MetaModels/core/blob/a176d53b23c17419d5e120c872a733f121864daf/src/FrontendIntegration/FrontendFilter.php#L394-L400

[zonky2]

Please note that you can now set the parameters yourself and also make a selection between GET and Slug.

[zonky2]

@stefanheimes create a new type of filter as "filter_pass_through"

[discordier]

Can't we add this to the filter module/element instead of adding a non functional filter?

On the given use case, we might want to add a custom "sorting filter" for the frontend, however, I am unsure how this will be integrated into the list and filter module workflow.