Remove Promtail Documentation

General MR

Summary

This started as just removing Promtail references in the docs, but became a bit of a small documentation cleanup effort.

General Summary:

• Removes references to Promtail in bigbang/docs and replaces with Alloy
• Updated Mermaid diagrams to refer to Alloy instead of Promtail
• Adds deprecation notice to Promtail package-architecture/promtail.md
• Removes older irrelevant documentation

Additional Cleanup:

• autoscaling-fluentbit-and-promtail.md moved to VPA repository as we do not want to advertise this package in Umbrella MR
  • VPA repository currently does not have a mission team assigned and has no maintainer.
• efk-plg-logging-migration.md re-written as logging.md
• Adds appliance-mode as a deployment scenario, and updates the doc/values to reference Alloy instead of Promtail
• Deletes training.md - Empty directory for 2+ years
• Deletes image-pull-policy.md - Not really a useful page
• Deletes ironbank-testing.md - Not a followed process anymore
  • Also has redundant information to https://repo1.dso.mil/big-bang/bigbang/-/blob/master/docs/developer/test-package-against-bb.md
• Deletes core-packages-1-x.yaml - Old 1.X values not useful
• Deletes git-repo-values.yaml - Not useful, redundant to our values.yaml

Relevant logs/screenshots

Linked Issue

Closes #2704 (closed)

Upgrade Notices

N/A