* standardise plot data output
* add data required for new anchors to renderer properties
* feed dvc-render updates into API output
* update --json --split api with new data types (send split anchor definitions as strings)
* accomodate zoom and pan anchor
* switch anchor_revs to revs_with_datapoints
* accomodate height and width anchors
* drop terrible idea of holding all data as strings
* fix plot having multiple x fields
* move inferred properties off vega converter class
* 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