Chore: Rewrite alerting css using object styles

[kaydelaney]

If any reviewers would prefer for this PR to be broken up into several smaller ones let me know!

Edit: Some details for context

The process for converting the style formats was as follows:

1. Ran a grep for any ts/tsx/js/jsx files with a match for "css`"
2. Wrote a very hacky deno script to do some text processing on the matched files
3. Ran yarn start, checking for any failures or type issues (sometimes this surfaced issues with the original css, which I then fixed)
4. Ran prettier on any changed files to fix up the formatting
5. Went through each file the script couldn't handle. Typically the files in question were ones with multi-line conditional logic or ones that used css selectors.
6. Manually fixed the styles for any classes that were causing problems, and then re-ran the script to catch the simple cases.
7. Reviewed each of the changed files one by one to make sure there weren't any mistakes.

For completeness, here's the script I wrote: https://gist.github.com/kaydelaney/489bac318fe99febd7d0cf3e40b2071b
(Don't judge it too harshly 🙏 )

[gillesdemey]

Fixed the merge conflicts from #84501 :)

[gillesdemey]

Thanks for putting in all of the work @kaydelaney!

Haven't reviewed all the changes but we've agreed to just go ahead and stamp this for approval – the Alerting team will keep on eye on any weird or odd style changes and we'll just fix them as they come.

I've taken the PR for a quick spin and no major functionality seems impacted :)

LGTM!