conv1d, special case

Summary:
We follow D50914117 to implement a specific case of conv1d for our needs. Specifically, we require
- the input tensor to have a single batch
- groups == in_channels == out_channels
- weight_sizes.at(1) == 1
- stride == 1
- padding == 0
- dilation == 1

We assume `bias==True`. The `bias==False` case in handled in the next diff.

General cases and optimizations will be enabled later.

Reviewed By: jorgep31415

Differential Revision: D56220143

fbshipit-source-id: a18de3a463875b9617cb7930febf7622fe866536