Support for MPIJob scheduling

[mimowo]

What would you like to be added:

Support for scheduling of MPIJob, controller by the MPI-operator (https://github.com/kubeflow/mpi-operator).

The decision for the integration to be part of the Kueue project was discussed here: kubeflow/mpi-operator#505 and here: kubeflow/mpi-operator#521 (comment).

Why is this needed:

Users of the MPI operator would like to use Kueue without a need for refactoring. Also, the integration with MPI operator will be the first for Kueue so will pave the way for integrations with other frameworks.

Completion requirements:

This enhancement requires the following artifacts:

• Design doc
• API change
• Docs update

The artifacts should be linked in subsequent comments.

[mimowo]

/assign

[tenzen-y]

@mimowo Should we use #65?

[mimowo]

Deduplicating as there is already #65, @tenzen-y thanks for pointing this out.