WIP next revision of the reference section of the docs (DOCS-4891)

[MichaelDrogalis]

A new draft of the reference section.

[MichaelDrogalis]

@JimGalasyn Can I get a review of overview/apache-kafka-primer.md? I think this content will be useful to link to in other parts of the docs, including what we're working on here.

[JimGalasyn]

@MichaelDrogalis Looks great, I gave it a quick copy edit in https://github.com/confluentinc/ksql/pull/5977.

[MichaelDrogalis]

@JimGalasyn Thanks!

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