Loihi 2 backend support for parallel OptimizationSolver

[GaboFGuerra]

User Story

As a user of the OptimizationSolver I want to run the Loihi2 Optimization solver with many parallel configurations running simultaneously to get higher solution probability and a lower time to solution.

Conditions of satisfaction

• User can explicitly invoke the number of parallel copies of the solver network in SolverConfig.
• At runtime, the network state is read from the network with the best cost.
• The user can give the solver a set of hyperparameters in SolverConfig which parameterize each copy of the network solver.

Acceptance Tests

With Loihi 2 backend:

• Number of parallel copies of the network in SolverConfig results in an equivalent number of SNN + CostIntegrator copies on the SolverProcess and SolverModel.
• ReadGate's RefPorts for solution readout and spike counters for cost reading are equal the number of copies of the network.
• Solver network and solution readout processes are correctly connected.
• The input set of hyperparameters are correctly propagated and distributed into the solver network copies.
• At runtime, the network state is read from the network with the best cost.

Lava version:

• [x] 0.3.0 (feature release)

I'm submitting a ...

• [x] feature request

Other information:

insert the output from lava debug here