Issue #2873777 by maxilein: Validation requiring a data field prevents the selection of the "chart" style formatter from the views/add page

Issue #2972880 by andileco: Enable suffix and prefix on Highcharts Y-Axis labels without ruining formatting

Issue #2971703 by mikolos: Selecting "Chart" as format results in Warning: Invalid argument supplied for foreach()

Issue #2962561 by andileco: Work to eliminate the charts.pages.inc file by adopting a stronger OOP approach

Add code documentation and rename variables in template_preprocess_views_view_charts. This also removed the unused ChartsRenderInterface class.

Issue #2953953 by Grimreaper: Module dependency to the chart plugin's module not added in the view config

Remove ModuleSelector, which was no longer being used in favor if plugins; make adjustments to the Chart Attachment display plugin to make it inherit more from Core; make some title and legend positioning changes for Highcharts

Issue #2953912 by andileco: Undefined index exporting in Drupal\charts_highcharts\Plugin\chart\Highcharts->buildVariables line 205

Issue #2953102: Highcharts pie/donut charts should be able to accommodate one node (or an aggregation) with multiple fields