Use the jsoncons non-throwing versions of decode for cbor and ubjson

[Ian-Flury]

• Remove jsoncons::decode_* in favor of jsoncons::try_decode_*.
• Addresses Issue 429

[gemini-code-assist]

Summary of Changes

Hello @Ian-Flury, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request refactors the CBOR and UBJSON decoding logic to utilize non-throwing versions of the jsoncons library functions. This change enhances the robustness and predictability of error handling by moving away from exception-based mechanisms towards a more explicit Result type pattern. The update also includes corresponding modifications to test cases to ensure the new error handling behavior is correctly validated.

Highlights

• Non-throwing Decoding: The pull request replaces throwing jsoncons::decode_* functions with their non-throwing jsoncons::try_decode_* counterparts for CBOR and UBJSON parsing. This shifts error handling from try-catch blocks to checking the result.has_value() of the returned std::optional-like type.
• Improved Error Messaging: Error messages for parsing failures are now generated directly from the jsoncons library's error messages, providing more specific details about the parsing issue.
• Enhanced Test Coverage: New test cases have been added for both CBOR and UBJSON to specifically verify error messages for missing fields and type mismatches. Existing tests for decode errors have been updated to align with the new non-throwing error handling mechanism.
• Documentation Update: A minor update was made to the tests/README.md file to correctly specify the language for a shell code block.

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[gemini-code-assist]

Code Review

This pull request successfully replaces the exception-throwing decode_* functions with their non-throwing try_decode_* counterparts for both CBOR and UBJSON deserialization. This is a great improvement for error handling robustness. The corresponding tests have been updated to verify the new behavior, including checks for the new error messages and ensuring no exceptions are thrown. I've included a couple of minor suggestions to improve test code readability.