[CUDAQ-790] cc.device_call lowering to realtime dispatch for local simulators

[1tnguyen]

Support lowering of cc.device_call to realtime-based ring-buffer dispatch.

cc.device_call is lowered to three ABI calls that operate on a transport-neutral frame lease - a leased RX/TX slot pair owned by the runtime for the duration of one RPC:

  __cudaq_device_call_acquire_realtime_frame  // lease an in-flight frame
  __cudaq_device_call_dispatch_realtime_frame // publish + wait
  __cudaq_device_call_safely_release_realtime_frame

The compiler writes function arguments directly into the leased RX payload and reads results directly from the leased TX payload.

• Scalars are stored at aligned offsets in the request slot

• std::vector<T> args use a length prefix followed by element bytes packed in place.

• Output std::vector<T>& arguments (for CUDA-QX interop) are signalled via an attribute on cc.device_call and read back through the same zero-copy response slot.

  The runtime side (runtime/internal/device_call/) wraps cudaq_ringbuffer_t from CUDA-Q Realtime: a singleton driver routes per-device sessions to a DeviceCallChannel, with two built-in shared-memory channels: device_dispatch (persistent GPU dispatch kernel) and host_dispatch (graph-launch with a pinned mailbox).

Notes:

• This PR handles local shared-memory only; no process separation or RDMA transport in this branch. This is deferred to a follow-up.

• CUDA-Q builds without realtime by default; the path is opt-in via CUDAQ_REALTIME_DIR at configure time (points to a realtime installation) and

• CI here is build-only: realtime_integration_ci.yml compiles a realtime-enabled CUDA-Q against the realtime installation.

Tested by:

• DeviceCallDispatchTester.cu: test runtime ring-buffer / channel behavior
• End-to-end NVQPP/device_call_realtime_{scalar,array}.cpp tests of shared-memory and host-dispatch channels for different arguments and return type with simulators in the loop.

[github-actions]

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