improve HTML report loading performance

[jkeys089]

Description

This PR improves the loading performance for HTML reports.
Anecdotally, our largest features would refuse to load even after 20 minutes. After this change, they load in 5-10 seconds.

There are three main areas of improvement:

1. use vanilla JS in hot paths (since jQuery can sometimes be a bit slow)
2. utilize event delegation to avoid adding unneeded event listeners
3. defer loading / processing wherever possible (specifically, when identifying step child nodes during toggling and loading image comparison diff UI options lazily)

• Relevant Issues : New karate report has slow performance when selecting scenario from left side-bar #1270
• Relevant PRs : n/a
• Type of change :
  • New feature
  • Bug fix for existing feature
  • Code quality improvement
  • Addition or Improvement of tests
  • Addition or Improvement of documentation