Minor improvements to the performance bar

What does this MR do and why?

Minor improvements to the performance bar

There are some minor improvements that can be done on the performance bar. It has quite some legacy CSS that potentially causes all kind of weird side effects. Also there are are minor bugs and JS improvements as well:

• Replace a bit of color related CSS with utility classes
• Remove some deprecated CSS
• Use Vue APIs to hide footers on the modals instead of CSS
• Use Vue APIs to ensure modals do not auto-focus, so that they can be quickly closed with Esc in case they have a dropdown
• Fix backtrace functionality which is currently broken

Changelog: other

References

Please include cross links to any resources that are relevant to this MR. This will give reviewers and future readers helpful context to give an efficient review of the changes introduced.

• Spun off from !171948 (merged)

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Screenshots or screen recordings

Before	After
before	after

How to set up and validate locally

1. Activate the performance bar (keyboard shortcut p b)
2. Use it