Make AIS CLI installation optional
# What does this PR do ?

This PR makes installation of AIS CLI optional.

**Collection**: Dockerfile

# Changelog 
- Update `Dockerfile` to install AIS CLI only if `REQUIRE_AIS_CLI == true`
- Added an installer script for AIS CLI

# Usage
AIS CLI can be installed by setting `REQUIRE_AIS_CLI=true`, for example:

```bash
docker ... --build-arg REQUIRE_AIS_CLI=true
```

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