Allow selecting items in Workflow History Timeline

[adhityamamallan]

Summary

• Add onClickItem handler to Timeline that gets called when the VisJS Timeline registers a click on an item
• Add "id" number to TimelineItem
• Set selected event in query params and scroll to it when an item is selected in the timeline
• Refactor Workflow Timeline Styles to share common styles across different items and states
• Added rounding to non-timer items
• Removed rounding from timer items

Test Plan

Updated unit tests + ran locally.

Regular event group selected

Single event selected

Timer selected