[NLP] ArtifactItem with init=True to make it debuggable
jenkins > Thanks LGTM

Thanks! I've just rebased it, I'll merge once pipeline completes.
# What does this PR do ?

When debugging artifact items I struggled with `ArtifactItem` as it is defined with `init=False` which results in issues when printing an instance of this class.

The following minimal example illustrates the problem - this code
```
from dataclasses import dataclass


@dataclass(init=False)
class Point:
    x: int
    y: int

p = Point()
print(p)
```
results in **AttributeError: 'Point' object has no attribute 'x'**. So it doesn't make it easier to check what's going on.

**Collection**: [NLP]

# Jenkins CI
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**PR Type**:
- [x] Improvement


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# Additional Information
* Related to https://github.com/NVIDIA/NeMo/pull/7935
