DOC-5692 Deprecated/archived repos

[aimurphy]

Changes to this release only:

• Burnell is archived and doesn't seem to be used anymore. Removed one reference to it.
• pulsar-helm-chart is deprecated with KAAP as the replacement. This PR adds a note in some (not all) places where pulsar-helm-chart is mentioned. I didn't remove links or steps that use the deprecated repo.
• luna-streaming-examples is archived. I moved specific files from that repo into /attachments/ to remove the dependency on that repo.

Changes to all 4 pulsar-docs releases:

• change {product} Helm chart to {company} {pulsar-short} Helm chart.
• Remove unneeded ragstack-ai attributes from local-preview-playbook

[plpesvc-ds]

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[mendonk]

+1