Support for multi-channel audio data
Thanks @yunbin, we'll take a look at adding this functionality over the next couple weeks. We'll post future updates here. @anteju  Any update on getting the channel feature implemented in NeMo training scripts? @yunbin, please check #9007.
The change there enables using channel selector from manifest for `nvidia/canary-1b` model.
**Describe the bug**

NeMo training and decoding scripts do not support multi-channel audio data.  

**Steps/Code to reproduce bug**

It does not support specifying which channel to use  for each audio file in each line in train.manifest.json or test.manifest.json file. 

I was able to run  ./examples/asr/speech_to_text_eval.py with "channel_selector=" to specify the channel for all the audio in a manifest.json file, but I can't find a way to specifying them for each audio file inside the manifest.json file.




**Expected behavior**
 
Can NeMo team add this useful feature to work with a diverse set of multi-channel training and testing audio data so data from different channel can be mixed within a manifest.json file?

**Environment overview (please complete the following information)**

NeMo was installed by pip in a conda environment. It works for single channel audio data. 
 
 
