Akoumparouli/nemo ux tokenizer fix
# What does this PR do ?
1) make nemo2-ckpts self-contained https://github.com/NVIDIA/NeMo/pull/10351/files#diff-5fed9dcc17cd5128af7ed4f9228d37c1dcaa22bf052620cc0a59d196770d3acaR109 and https://github.com/NVIDIA/NeMo/pull/10351/files#diff-9d41499746a3f28bb941592bb19445c90a0baa974ee59c0c5c8d78eb6ec1db5bR31

2) fix a bug in tokenizer IO https://github.com/NVIDIA/NeMo/pull/10351/files#diff-f9d7e4a01855072a41a91e2a37c117f1a90d933aba0258036eeaabd130fc2b5bL240

3) add tokenizer restoration when loading from nemo2-ckpts https://github.com/NVIDIA/NeMo/pull/10351/files#diff-6cc360fb87bae4067befd052372e537754bdf079589dd10818307a1ba5778735R93
 
llama2, llama3 confirmed to work.

**Collection**: [Note which collection this PR will affect]

# Changelog 
- Add specific line by line info of high level changes in this PR.

# Usage
* You can potentially add a usage example below

```python
# Add a code snippet demonstrating how to use this 
```

# GitHub Actions CI

The Jenkins CI system has been replaced by GitHub Actions self-hosted runners.

The GitHub Actions CI will run automatically when the "Run CICD" label is added to the PR.
To re-run CI remove and add the label again.
To run CI on an untrusted fork, a NeMo user with write access must first click "Approve and run".

# Before your PR is "Ready for review"
**Pre checks**:
- [ ] 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
- [ ] 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)
