Two stage solution of VRPs using QUBO

[srrisbud]

Issue Number: #192

Objective of pull request: To enable solving VRPs using the QUBO solver in lava-optimization library

Pull request checklist

Your PR fulfills the following requirements:

• [x] Issue created that explains the change and why it's needed
• [x] Tests are part of the PR (for bug fixes / features)
• [x] PR conforms to Coding Conventions
• [x] Lint (pyb) passes locally
• [x] Build tests (pyb -E unit) or (python -m unittest) passes locally

Pull request type

Please check your PR type:

• [x] Feature

What is the new behavior?

• VRPSolver can solve VRPs using 2-stage QUBO strategy (clustering + TSPs)

Does this introduce a breaking change?

• [x] No