[STABLE ABI] Porting lfilter.cpp

[pearu]

This issue collects tasks that block porting lfilter.cpp to use torch stable ABI.

• implement mutable_data_ptr<T>() and const_data_ptr<T>() in torch/csrc/stable/tensor_struct.h. For instance, this simplifies porting of expressions like tensor.data_ptr<scalar_t>(). Currently, one needs to rewrite this as reinterpret_cast<scalar_t*>(tensor.data_ptr()) where tensor is a torch::stable::Tensor.
  Fix available: [STABLE ABI] Add mutable_data_ptr() and const_data_ptr() methods to torch::stable::Tensor. pytorch#161891
• can we use at::parallel_for in torch stable ABI code?
• implement unsqueeze as a stable/ops.h operation
• implement select as a stable/ops.h operation
• implement at::matmul as a stable/ops.h operation
• implement index_put_ as torch::stable::Tensor method or a stable/ops.h operation. Can we use torch::indexing::Slice() in torch stable ABI code?

^ @NicolasHug @scotts @janeyx99

[pearu]

See also #4023 that may reduce the task list.

[janeyx99]

can we use at::parallel_for in torch stable ABI code?

We need to write a header only version of this! I think there's something in progress cc @mikaylagawarecki

implement unsqueeze as torch::stable::Tensor method or a stable/ops.h operation

ops.h please! let's keep Tensor small

For the ops, let's attempt to use aoti_torch_call_dispatcher as much as we can!

Can we use torch::indexing::Slice() in torch stable ABI code?

ArrayRef is something we're working on, but what is the exact line for index_put? It may be faster/better to rewrite as other aten ops.

[vadimkantorov]

@janeyx99 Shouldn't lfilter and iir_cuda go upstream to core? (in torch.signal.* namespace - similar to scipy.signal) WDYT? It's probably useful even outside audio contexts