refactor: simplify normalize fielddef (#5156)
refactor: simplify normalize fielddef (#5156)


vega/vega-lite,uwdata/vega-lite,uwdata/vega-lite,uwdata/vega-lite,uwdata/vega-lite,vega/vega-lite,vega/vega-lite,vega/vega-lite,vega/vega-lite,uwdata/vega-lite