Update contribution documentation for guidelines to add a new test

[vinayada1]

Area for Improvement

The tests have now been separated for cloud and noncloud scenarios. This issue is for updating the contribution guidelines to add a new test based on the new test organization structure.

Observed behavior

No response

Desired behavior

Write documentation guidelines

Proposed Fix

No response

rad Version

0.32.0

Operating system

No response

Additional context

No response

Would you like to support us?

• Yes, I would like to support you

AB#12401

[radius-triage-bot]

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[radius-triage-bot]

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We also welcome community contributions! If you would like to pick this item up sooner and submit a pull request, please visit our contribution guidelines and assign this to yourself by commenting "/assign" on this issue.

For more information on our triage process please visit our triage overview

[sylvainsf]

The cloud vs non-cloud instructions should be added here:
https://github.com/radius-project/radius/blob/main/docs/contributing/contributing-code/contributing-code-tests/writing-functional-tests.md