The upstream pipewire config is written in an almost, but not quite
JSON format. The parser accepts standard JSON, though, so we don't
need to write our file in the same nonstandard version.
The typing for all config options is changed from `types.attrs`, which
behaves poorly when the option is set from multiple locations, to the
formats.json-type.
Also, rewrite some very long one-liners for improved readability.
