Core/FFI/Go: Add Support for Async and Sync Client Types in FFI

[barshaul]

✨ Summary

This PR introduces support for both asynchronous and synchronous clients across the Rust-C FFI boundary. It unifies command execution and error handling while allowing consuming languages to choose the interaction model that fits their needs. This PR establishes the groundwork required to support synchronous APIs in the Python wrapper.

✅ Key Changes

🔹 Rust (FFI Layer)

• Added ClientType enum (AsyncClient and SyncClient) to differentiate client behavior.
• Introduced CommandResult and CommandError to represent sync command results and failures.
• Updated FFI functions (command, request_cluster_scan, update_connection_password) to return *mut CommandResult for sync support to immediately return result.

🔹 Go

• Updated createClient to pass the encoded ClientType to the Rust layer.

🔹 Tests

• Validated behavior for both client types via shared test logic.

🧠 Motivation

• Allows consuming languages like Go or Python to choose between blocking (sync) and callback-based (async) client interactions.

Issue link

This Pull Request is linked to issue (URL): #3457

Checklist

Before submitting the PR make sure the following are checked:

• This Pull Request is related to one issue.
• Commit message has a detailed description of what changed and why.
• Tests are added or updated.
• CHANGELOG.md and documentation files are updated.
• Destination branch is correct - main or release
• Create merge commit if merging release branch into main, squash otherwise.

[Yury-Fridlyand]

Keep in mind that go client is completely sync (even though it uses async backend from glide core).

[avifenesh]

Keep in mind that go client is completely sync (even though it uses async backend from glide core).

Can you explain the meaning in this context? Do you mean that there's no callbacks?

[Yury-Fridlyand]

This change is no-op for go client. It is sync already.
There are no plans to rewrite it using sync core API neither make an async implementation.