Gemma4 initial npu support

[cavusmustafa]

• Static shape fix for npu (some n_tokens dimensions were not detected)
• NPU fold was producing dynamic shapes due to slice ops. In certain cases like gemma4 architecture, they are replaced by split ops.
• A temporary fix for fp16 overflow issue on NPU using CLAMP before GELU.

[wine99]

CI openvino_gpu_low_perf failed

/home/llamauser/actions-runner-ravi9/_work/llama.cpp/llama.cpp/ggml/src/ggml-openvino/openvino/op/view.cpp: In function ‘ov::OutputVector ov::frontend::ggml::op::translate_view(const ov::frontend::ggml::NodeContext&)’:
/home/llamauser/actions-runner-ravi9/_work/llama.cpp/llama.cpp/ggml/src/ggml-openvino/openvino/op/view.cpp:80:12: error: unused variable ‘stride_at_dim’ [-Werror=unused-variable]
   80 |     size_t stride_at_dim = (slice_dim < static_cast<int>(ndims) - 1) ?
      |            ^~~~~~~~~~~~~
cc1plus: all warnings being treated as errors