[Docs migration] Cleans up investigation tools files - pt 2

[nastasha-solomon]

Addresses part of #559 by doing the following:

• Removes raw migrated Serverless files that are no longer being used.
• Adds anchors where missing and updates anchors that start with an underscore.
• Makes minor inline adjustments to the files that were labeled as "lift-and-shift" where appropriate.

Affected pages:

• Notes
• Cases
  • Cases requirements
  • Open and manage cases
  • Configure case settings

[benironside]

Found a few minor things but overall looks great!