feat: introducing the experimental package and refactoring test structure

[terrykong]

What does this PR do ?

Introduces experimental directory structure for code and docs. As part of the restructuring, the tests are moved closer to the source to reduce the repetition of directory structure.

Before

NeMo-Aligner/
├── docs/
│   └── user-guide/
│       └── ppo.html
├── nemo_aligner/
│   ├── algorithms/
│   └── data/
│       └── datasets.py
└── tests/
    ├── test_datasets.py
    └── functional/
        └── test_cases/
            └── dpo-llama3

Proposal

NeMo-Aligner/
├── docs/
│   ├── user-guide/
│   │   └── ppo.html
│   └── user-guide-experimental/    <----- experimental docs
│       └── new-thing.html
├── nemo_aligner/
│   ├── algorithms/
│   ├── data/
│   │   ├── datasets.py
│   │   └── tests/
│   │       └── datasets_test.py
│   └── experimental/               <----- experimental sub-package
│       ├── <proj-name>/
│           ├── dataset.py          <----- experimental dataset
│           ├── new_algo.py         <----- experimental algo
│           ├── model.py            <----- experimental model
│           └── tests/
│               └── model_test.py   <----- experimental model test
└── tests/
    └── functional/
        └── dpo.sh
        └── test_cases/
            └── dpo-llama3
    └── functional_experimental/    <----- experimental functional tests (mirrors functional/ structure)
        ├── new_algo.sh
        └── test_cases/
            └── new_algo-llama3

• By moving the docs out of the main dir, we can control what is rendered in the NeMo docs
• colocating the tests in the same package makes it easier to find tests and reduces number of mirrored dirs
  • these can be filtered out when we publish to pypi (Needs more investigation)
• functional tests will stay outside for convenience

[terrykong]

@ko3n1g Tried excluding the test files via Manifest.in/exclude_package_data, but both don't seem to work when building a sdist wheel or simply pip install .

[odelalleau]

Looks mostly good to me, just a few questions below, and one suggestion: I think it'd be better to have tests of experimental features under a dedicated folder, so that we can easily identify them. Either under tests/functional/experimental, or tests/experimental, or tests/functional_experimental for instance.

[terrykong]

I think it'd be better to have tests of experimental features under a dedicated folder, so that we can easily identify them. Either under tests/functional/experimental, or tests/experimental, or tests/functional_experimental for instance

@odelalleau Makes sense! Please see 2893053

[odelalleau]

@odelalleau Makes sense! Please see 2893053

Looking good, thanks!

[ko3n1g]

great change, thanks!