Guidance for explaining a command or elements in a code block instead of callouts

[Preeticp]

We can not use callouts in code blocks for the following reasons:

• Callouts are not supported in DITA: Unlike AsciiDoc, DITA does not support callouts as a method to add annotations to specific lines in verbatim blocks.
• Callouts do not work for AI: Because callouts are not supported in DITA, (and we're not making changes to DITA-OT) there isn't semantic markup for an AI agent to understand what is happening or to output that semantic markup properly.
• Callouts are not used by our competitors: See: Competitor analysis on callouts and code blocks

Currently in our documentation we use callouts for the following use cases:

• Use Case 1: Add relevant additional information about a single line of code, element, or variable.
  

• Use Case 2: Add relevant additional information about multiple lines of code, elements, or explain the structure of a sample YAML file
  

• Use Case 3: Provide information on placeholders/variables
  

• Use Case 4: Notes about a particular line in the code

We need to ensure that the SSG has updated guidance on replacing callouts with simple sentences, bulleted/unordered lists, definition lists or Admonition style as appropriate depending on context.

[IngridT1]

@Preeticp As we discussed yesterday, this would be a high severity level, so it would receive extra attention. Because we don't have an SLA (Service Level Agreement) in place, we don't have specific time frames or anything. But if you put a PR together, I'll review it tomorrow with @bburt-rh and make sure it will merge cleanly. I might have a few comments or changes of my own. But I should be able to get this done in the next day or 2.

[Preeticp]

@IngridT1, ack. Thanks to both you and Brian.
Here's the PR: #541 please let me know if any changes are required.