Update for NEST release
<!-- pylint-output-strict-mode-true -->

beep boop 🤖: 🚨 The following files must be fixed before merge!

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Your code was analyzed with PyLint. The following annotations have been identified:

```

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Your code has been rated at 10.00/10
```

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Thank you for improving NeMo's documentation! <!-- pylint-output-strict-mode-false -->

beep boop 🤖: 🙏 The following files have warnings. In case you are familiar with these, please try helping us to improve the code base.

---

Your code was analyzed with PyLint. The following annotations have been identified:

```
************* Module nemo.collections.asr.models.ssl_models
nemo/collections/asr/models/ssl_models.py:64:0: C0301: Line too long (142/119) (line-too-long)
nemo/collections/asr/models/ssl_models.py:65:0: C0301: Line too long (145/119) (line-too-long)
nemo/collections/asr/models/ssl_models.py:71:0: C0301: Line too long (143/119) (line-too-long)
nemo/collections/asr/models/ssl_models.py:72:0: C0301: Line too long (147/119) (line-too-long)
nemo/collections/asr/models/ssl_models.py:618:0: C0301: Line too long (122/119) (line-too-long)
nemo/collections/asr/models/ssl_models.py:521:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/collections/asr/models/ssl_models.py:564:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/collections/asr/models/ssl_models.py:597:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/collections/asr/models/ssl_models.py:753:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/collections/asr/models/ssl_models.py:776:4: C0116: Missing function or method docstring (missing-function-docstring)
************* Module nemo.collections.asr.modules.ssl_modules.multi_layer_feat
nemo/collections/asr/modules/ssl_modules/multi_layer_feat.py:27:0: C0115: Missing class docstring (missing-class-docstring)
nemo/collections/asr/modules/ssl_modules/multi_layer_feat.py:84:0: C0115: Missing class docstring (missing-class-docstring)
nemo/collections/asr/modules/ssl_modules/multi_layer_feat.py:162:0: C0115: Missing class docstring (missing-class-docstring)
************* Module nemo.core.classes.modelPT
nemo/core/classes/modelPT.py:82:0: C0301: Line too long (130/119) (line-too-long)
nemo/core/classes/modelPT.py:177:0: C0301: Line too long (121/119) (line-too-long)
nemo/core/classes/modelPT.py:184:0: C0301: Line too long (154/119) (line-too-long)
nemo/core/classes/modelPT.py:258:0: C0301: Line too long (131/119) (line-too-long)
nemo/core/classes/modelPT.py:262:0: C0301: Line too long (132/119) (line-too-long)
nemo/core/classes/modelPT.py:310:0: C0301: Line too long (160/119) (line-too-long)
nemo/core/classes/modelPT.py:390:0: C0301: Line too long (135/119) (line-too-long)
nemo/core/classes/modelPT.py:1241:0: C0301: Line too long (123/119) (line-too-long)
nemo/core/classes/modelPT.py:1478:0: C0301: Line too long (140/119) (line-too-long)
nemo/core/classes/modelPT.py:1689:0: C0301: Line too long (128/119) (line-too-long)
nemo/core/classes/modelPT.py:1708:0: C0301: Line too long (135/119) (line-too-long)
nemo/core/classes/modelPT.py:1718:0: C0301: Line too long (122/119) (line-too-long)
nemo/core/classes/modelPT.py:1844:0: C0301: Line too long (166/119) (line-too-long)
nemo/core/classes/modelPT.py:1913:0: C0301: Line too long (120/119) (line-too-long)
nemo/core/classes/modelPT.py:2067:0: C0301: Line too long (151/119) (line-too-long)
nemo/core/classes/modelPT.py:223:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/core/classes/modelPT.py:869:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/core/classes/modelPT.py:935:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/core/classes/modelPT.py:939:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/core/classes/modelPT.py:946:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/core/classes/modelPT.py:1214:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/core/classes/modelPT.py:1638:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/core/classes/modelPT.py:1756:4: C0116: Missing function or method docstring (missing-function-docstring)

-----------------------------------
Your code has been rated at 9.83/10
```

---

Thank you for improving NeMo's documentation!
# What does this PR do ?

1. Add script for extracting embeddings from different layers of NEST model (also works for other Conformer-based models). 
2. Fixes ModelPT.py when defer_setup is True, since the current code will skip builing validation dataloaders as they are lists and not None.
3. Update ASR manifest processor to allow `duration=None`
4. Minor documentation update.


**Collection**: [asr,core]
