[FEATURE] Support Jumanji's MultiCVRP

[OmaymaMahjoub]

Feature

Adding a wrapper for jumanji's MultiCVRP. The motivation for this, is to support more environments that closely align with real-world applications.

Proposal

A good starting point would be to update the existing non maintained PR.

Testing

Integrate the environment into the list of envs to test in the integration_test.py and make sure it works fine.

Benchmarking

Benchmark the performance of the existing algorithms on MultiCVRP.
[Optional] Create a README file to document the benchmark results.