gl-sdk: Add C++ bindings

[ardier16]

Adds C++ bindings support to gl-sdk:

• Introduce a cpp-bindings feature and C++ compatible resolve_input export.
• Add task sdk:bindings-cpp and include it in task sdk:bindings-all.
• Use uniffi-bindgen-cpp plus perl post-processing to rename generated register identifiers to register_node.
• Update the SDK README with C++ bindings setup and generation instructions.

[cdecker]

Excellent addition @ardier16, thank you 🙏

Can we add a generation run in CI as a followup, so we can ensure that the CPP stub generation works as expected, and we don't accidentally break it?

[cdecker]

We can make the entirety of the API sync, and then running async code inside of the Rust crate only. This would mean all the APIs are the same regardless of the host language are sync-only.

[cdecker]

I'll do this in a followup PR. As @ardier16 pointed out in a call this is a breaking change, and together with #716 we will bump version to 0.4 once this is merged.