Enable problem-level parallelism for OptimizationSolver

[AlessandroPierro]

User story

As a user, I want to be able to solve multiple optimization problems in parallel with the OptimizationSolver.

Conditions of satisfaction

• Problem level parallelism is enabled on CPU backed along. It runs concurrently with hyperparameter level parallelization

Acceptance tests

Tasks

• [x] Rethink UI to make solver easy for the user
• [x] Make changes and add new helper functions to the builder.py to accommodate for these changes
• [x] Make changes to the solution reader
• [x] Adapt the read_gate model for the multiple problems
• [ ] Adapt the solution_readout model for multiple problems
• [ ] Adap OptimizationSolver to get the solution from multiple problems