2441: Add multiselect chart for group performance in analytics

[KralMarko123]

Feature for #2441

• Vendored chart.js and regression.js
• Added new route, controller, and view to serve as a place for using new chart logic
• Added multiselect_component.rb which is a multiselectable dropdown (was introduced and tested in 2258: Share tags to organizations #2409)
• Extended analytics_filter_controller.js to update multiselect component when dependent dropdowns are modified
• Added a performance chart where users can select multiple groups on a single canvas
• Added charts_download_controller.js stimulus controller for downloading images of chart