CLOUDP-294902: Support listing private preview values

[blva]

Proposed changes

Jira ticket: CLOUDP-294902

I think I added both supports so I'm adding more testing and some error handling

Happy cases

➜  cli git:(CLOUDP-294902) ✗ ./bin/foascli versions -s test/data/base_spec_with_private_preview.json
[
  "2023-01-01",
  "2023-02-01",
  "2023-10-01",
  "2023-11-15",
  "2024-05-30",
  "2024-08-05",
  "2024-10-23",
  "2024-11-13",
  "2025-05-30",
  "2043-01-01",
  "private-preview-new-feature"
]

➜  cli git:(CLOUDP-294902) ✗ ./bin/foascli versions -s test/data/base_spec_with_public_preview.json 
[
  "2023-01-01",
  "2023-02-01",
  "2023-10-01",
  "2023-11-15",
  "2024-05-30",
  "2024-08-05",
  "2024-10-23",
  "2024-11-13",
  "2025-05-30",
  "2043-01-01",
  "preview"
]

Errrors / linting

➜  cli git:(CLOUDP-294902) ✗ ./bin/foascli versions -s test/data/base_spec_with_public_preview.json
failed to parse preview version name: invalid value for 'public' field, only 'true' or 'false' are allowed
Error: invalid value for 'public' field, only 'true' or 'false' are allowed

Checklist

• I have signed the MongoDB CLA
• I have added tests that prove my fix is effective or that my feature works

Changes to Spectral

• I have read the README file for Spectral Updates

Further comments

[andreaangiolillo]

LGTM