Alias Swish to SiLU 
This pull request **introduces 1 alert** when merging 7b5bebeebaca9a722f2ab6b3b1ea8947aa99fa8b into f7d3a72e1b5da664e5e1c5ac0855a9e29d32601d - [view on LGTM.com](https://lgtm.com/projects/g/NVIDIA/NeMo/rev/pr-29052614e94cdee0d929259ae93e0a7126cc6347)

**new alerts:**

* 1 for Unused import
# Changelog
- Alias `Swish` activation to `nn.SiLU` which is mathematically identical
- Update activations to inplace execution if possible for `ConvASREncoder`

Signed-off-by: smajumdar <titu1994@gmail.com>