Fix and refactor label models
# What does this PR do ?

Fix and refactor label models

**Collection**: ASR

# Changelog 
- fix hanging issue happens in test after train in` speech_to_label.py `, `speaker_reco.py` and `speaker_reco_finetune`.py
- fix weighted cross entropy by disabling cal_label_occurences for val and test
- refactor loss instantiation part in label_models 
- updated yamls file for above refactory.

# Usage
Specify loss as below in config files for label_models
```python
loss:
    _target_: nemo.collections.common.losses.cross_entropy.CrossEntropyLoss
    weight: 'auto' # could be 'auto' or 1D tensor or null
# or
loss:
    _target_: nemo.collections.asr.losses.angularloss.AngularSoftmaxLoss # you could also use cross-entrophy loss
    scale: 30
    margin: 0.2
    
```
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**Pre checks**:
- [x] Make sure you read and followed [Contributor guidelines](https://github.com/NVIDIA/NeMo/blob/main/CONTRIBUTING.md)
- [ ] Did you write any new necessary tests?
- [ ] Did you add or update any necessary documentation?
- [ ] Does the PR affect components that are optional to install? (Ex: Numba, Pynini, Apex etc)
  - [ ] Reviewer: Does the PR have correct import guards for all optional libraries?
  
**PR Type**:
- [ ] New Feature
- [x] Bugfix
- [ ] Documentation

If you haven't finished some of the above items you can still open "Draft" PR.


## Who can review?

Anyone in the community is free to review the PR once the checks have passed. 
[Contributor guidelines](https://github.com/NVIDIA/NeMo/blob/main/CONTRIBUTING.md) contains specific people who can review PRs to various areas.

# Additional Information
* Related to # (issue)
