docs: Fix documented Oracle NCLOB sample

[nj1973]

Description of changes

This PR adds tests for the documented Oracle LOB samples. From having these tests we found that the NCLOB sample was wrong so this PR also fixes the documentation.

Issues to be closed

Closes #1814

Checklist

• I have followed the CONTRIBUTING Guide.
• I have commented my code, particularly in hard-to-understand areas
• I have updated any relevant documentation to reflect my changes, if applicable
• I have added unit and/or integration tests relevant to my change as needed
• I have already checked locally that all unit tests and linting are passing (use the tests/local_check.sh script)
• I have manually executed end-to-end testing (E2E) with the affected databases/engines

[nj1973]

/gcbrun

[renzokuken]

LGTM. Good catch on DBMS_CRYPTO not being universal