Unit tests for PrngService

[Otaiki1]

Context

PRNG should be deterministic and unbiased.

Goal

Add tests for randomness distribution and seeding.

Contributor guide

1. Directory: oracle/
2. Verify same input produces same output.
3. Run basic statistical tests for bias on large sample.
4. Test with various request_ids and nonces.
5. Assert output length matches contract requirements.

References

• PRNG testing best practices.

[Zarmaijemimah]

@Zarmaijemimah has applied to work on this issue as part of the Stellar Wave Program's 3rd wave.

I can handle this issue and will love to work on it please kindly assign thank you.

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