Add the option for multiple views loading

[vigji]

Description

This PR attempts at defining a loading mode for supporting multi-camera data.

• [ ] Bug fix
• [ x] Addition of a new feature
• [ ] Other

This kind of data structure would be needed by anyone in the process of extracting 3D poses. This is something needed only as long as you do not have yet 3D coordinates, in my case (but I assume in anyone's) the end goal of having multiple views. So, if you want to support only the final, "clean" data where some triangulation of sort already happened, I would understand!

References

Discussion started in #196

How has this PR been tested?

Currently in the process of defining tests, atm just with already existing data, pretending it to be multi-camera.

Is this a breaking change?

If we decide to approve this, it will require some core redefinition in the dataset validator. Currently it seems to be quite strict; if the view dimension ends up being optional, it would require some work in the Validator class. I am not familiar with the processing functions to compute kinematics, in principle I assume the semantic indexing of xarray should allow for a smooth handling of this optionality - but I am not yet an xarray pro

Does this PR require an update to the documentation?

If accepted, yes.

If any features have changed, or have been added. Please explain how the documentation has been updated.

No changes yet

Checklist:

• [ x] The code has been tested locally
• [ ] Tests have been added to cover all new functionality
• [ ] The documentation has been updated to reflect any changes
• [ ] The code has been formatted with pre-commit

[sonarcloud[bot]]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
0.0% Duplication on New Code

See analysis details on SonarCloud

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 99.68%. Comparing base (426003c) to head (9a57287).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #197 +/- ## ======================================= Coverage 99.68% 99.68% ======================================= Files 11 11 Lines 638 643 +5 ======================================= + Hits 636 641 +5 Misses 2 2 ```

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[niksirbi]

Cross-linking this thread on Zulip, where we are discussing matters relevant to this PR.