module-filter-chain: allow loading configuration from JSON files

Improvements for wireplumber!412 (merged)

This will help delivering a better way to create such configurations. If /... or ~... is passed, then it's certainly not a JSON, then load the file. We don't want to support relative paths as we don't know where to find those. WP should take care of relative paths in such a case.

Also an improvement could be made to FIR loading method. Currently we have a WAV file parsing through libasound and this adds the need to have a separate (though software-agnostic) folder like /usr/share/sound-filters/vendor/product to store those WAVs. I find WAV to be not the most logical format to store filter data, as those are not sound data really, so we can just pass a JSON array of float numbers into the convolver via the config as an option. If that's welcome, I can contribute.