Add Unreal Result type to support C++ and Blueprint

[JasonAtClockwork]

Description of Changes

• Updated Unreal codegen to work with ::Result to match how ::Option works to create a new struct for each type pair identified
• Added new integration tests to confirm Ok state for all new types added to sdk-tests
• Added new UE_SPACETIMEDB_RESULT macro to capture de/serialization for the new structs

API and ABI breaking changes

N/A

Expected complexity level and risk

2 - Added new type generated from Result which creates new structs for each one identified

Testing

• Updated the integration tests to include the new Result types