Support tuple newtype patterns across SDKs

This issue tracks reimplementing the work from stale PR #2957, which has been closed because it is too far out of date to merge directly.

Original pull request

• PR #2957: Implemented newtype pattern support for tuples
• Original author: @egormanga

What the original PR was trying to do

Description of Changes Related issues: 2379, 2604, 4031. To be able to do this: (previously, the derive macro would panic.) This is an early attempt! I need help in figuring out all details on how to properly implement deserialization. Also, currently this fails with errors like these: (resolved) API and ABI breaking changes Unknown. Expected complexity level and risk 3? Testing - [x] SpacetimeDB compiles - [x] The module builds - [x] Publishing works

Closure context

• @egormanga what types does this generate in C#, TypeScript, and Rust? I think we'd need those to have support before we merge this. I am going to close this PR and open a ticket with you as the assignee.

If you are motivated to get this feature in then we'd need a philosophy for languages that don't have tuples or tuple structs. In particular C# and C++. Something like regular product types with field names like _0, _1, etc could be acceptable.

Reimplementation notes

• Reimplement this work on top of current master in a new PR.
• Keep the original PR linked as historical context and as a source of useful implementation ideas where still relevant.

Start by reviewing historical PR #2957 and comparing its approach with current master. Trace how tuple newtypes are represented across the Rust, C#, TypeScript, and C++ SDKs, including the language-specific philosophy for tuple-like types. Done means the feature works consistently across the SDKs and the module builds and publishes successfully.