Make TerminalSolver interface & ExperimentSolver class sealed

[AzureAaron]

Also made the ExperimentSolver class sealed.

[kevinthegreat1]

I don't get the point of making all the subclasses non-sealed. They shouldn't be extended anyways?

[AzureAaron]

I don't get the point of making all the subclasses non-sealed. They shouldn't be extended anyways?

Make them final instead?

[kevinthegreat1]

I didn't realize you have to put either non-sealed or final. That's really stupid and makes me think that we don't need this at all. But you can choose either non-sealed or final, I don't really care then.

[AzureAaron]

I didn't realize you have to put either non-sealed or final. That's really stupid and makes me think that we don't need this at all. But you can choose either non-sealed or final, I don't really care then.

I swapped them to final as they should not be extended.