[quant][fx] Add RNN reference module (#73386)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/73386
This PR adds support for RNN reference module, following https://github.com/pytorch/rfcs/blob/master/RFC-0019-Extending-PyTorch-Quantization-to-Custom-Backends.md
This includes: RNNCell, LSTMCell, GRUCell, LSTM
Test Plan:
will be tested in the lowering flow in a separate PR
Imported from OSS
Reviewed By: vkuzo
Differential Revision: D34469445
fbshipit-source-id: 71a13d7d056f7aaccdd98fb477c8a3a38aecc249
(cherry picked from commit 0b10f0d127515556b677eae3150f026ac8cd9acd)
