Follow-up from "Add after_script timeout details"

From the notes below, we should split up the before/after script sections, and perhaps expand the details about timeouts in after script, as well as any additional details necessary.

The following discussions from !21376 (merged) should be addressed:

• @marcel.amirault started a discussion: (+1 comment)

  @JonstonChan Yup, I verified it myself just now (it was supposed to add one more line after sleep, which it didn't, so it timed out):

  

  @steveazz Quick question: Is this intentional (job succeeding even if after_script times out)? There's also no time out message...

• @steveazz started a discussion: (+1 comment)

  @marcel.amirault this shouldn't be part of this MR, but maybe it's worth considering that we should split before_script & after_script into their own section, with more information it's becoming harder to read overall 🤔