P2p chunk size setting in nemo 2.0
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beep boop 🤖: 🙏 The following files have warnings. In case you are familiar with these, please try helping us to improve the code base.

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

```
************* Module nemo.lightning.run.plugins
nemo/lightning/run/plugins.py:33:0: C0301: Line too long (144/119) (line-too-long)
nemo/lightning/run/plugins.py:75:0: C0301: Line too long (145/119) (line-too-long)
nemo/lightning/run/plugins.py:127:0: C0301: Line too long (174/119) (line-too-long)
nemo/lightning/run/plugins.py:203:0: C0301: Line too long (150/119) (line-too-long)
nemo/lightning/run/plugins.py:65:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/lightning/run/plugins.py:105:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/lightning/run/plugins.py:150:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/lightning/run/plugins.py:213:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/lightning/run/plugins.py:265:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/lightning/run/plugins.py:284:4: C0116: Missing function or method docstring (missing-function-docstring)

-----------------------------------
Your code has been rated at 9.16/10
```

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

Add the env var (`NCCL_P2P_NET_CHUNKSIZE`) that adjusts P2P communication chunk size to nemo 2.0, which is critical to unload the buffering time from NCCL kernel execution time.

# Changelog 
Added `NCCL_P2P_NET_CHUNKSIZE` nemo 2.0 env var plugin

# Usage
Set `nccl_pp_comm_chunksize` in `PerfEnvPlugin`.


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