Update tests for org, usage, and keys, and remove old generated files

[nmuesch]

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• The pull request must only fix one issue, or add one feature, at the time.
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What does this PR do?

This PR updates the test files for the Keys, Orgs, and Usage endpoints to reflect their new schema names.
This also deletes the unused models that won't be part of the next generation

Review checklist (to be filled by reviewers)

• Feature or bug fix MUST have appropriate tests (unit, integration, etc...)
• PR title must be written as a CHANGELOG entry (see why)
• Files changes must correspond to the primary purpose of the PR as described in the title (small unrelated changes should have their own PR)
• PR must have one changelog/ label attached. If applicable it should have the backward-incompatible label attached.
• PR should not have do-not-merge/ label attached.
• If Applicable, issue must have kind/ and severity/ labels attached at least.