Add C++ runtime for speech enhancement GTCRN models (#1977)

See also https://github.com/Xiaobin-Rong/gtcrn

sherpa-onnx/csrc/offline-speech-denoiser-impl.h

@@ -0,0 +1,33 @@
+// sherpa-onnx/csrc/offline-speaker-speech-denoiser-impl.h
+//
+// Copyright (c)  2025  Xiaomi Corporation
+
+#ifndef SHERPA_ONNX_CSRC_OFFLINE_SPEECH_DENOISER_IMPL_H_
+#define SHERPA_ONNX_CSRC_OFFLINE_SPEECH_DENOISER_IMPL_H_
+
+#include <memory>
+
+#include "sherpa-onnx/csrc/offline-speech-denoiser.h"
+
+namespace sherpa_onnx {
+
+class OfflineSpeechDenoiserImpl {
+ public:
+  virtual ~OfflineSpeechDenoiserImpl() = default;
+
+  static std::unique_ptr<OfflineSpeechDenoiserImpl> Create(
+      const OfflineSpeechDenoiserConfig &config);
+
+  template <typename Manager>
+  static std::unique_ptr<OfflineSpeechDenoiserImpl> Create(
+      Manager *mgr, const OfflineSpeechDenoiserConfig &config);
+
+  virtual DenoisedAudio Run(const float *samples, int32_t n,
+                            int32_t sample_rate) const = 0;
+
+  virtual int32_t GetSampleRate() const = 0;
+};
+
+}  // namespace sherpa_onnx
+
+#endif  // SHERPA_ONNX_CSRC_OFFLINE_SPEECH_DENOISER_IMPL_H_