* plots: vega: converter: support multi series data split and props inference
Fixes: #7754, #8399
Related: iterative/studio#4369
* plots: converter: make converter infer x and y labels if not provided
* plots: vega: converter: roll back to datapoints format
* plots: vega: converter: refactor
* plots: infer labels on
* plots: get_plot_id: fix naming
* plots: vega: converter: notes regarding converting