Convert all .in input files to .json

[mrp089]

Problem

We added support for JSON input files in d98fd52. However, our tests are still in the legacy .in format.

Solution

Convert all test cases to JSON.

Additional context

Try some AI tools to create a Python converter .in -> .json and add it to the repository.

Code of Conduct

• I agree to follow this project's Code of Conduct and Contributing Guidelines

[arsLibera]

Can use the C++ executable to convert the legacy files to JSON using the appropriate input flags, e.g.,

svOneDSolver -legacyToJson "<inputFileName>.in" "<jsonInputFile>.json"

Also, the current system tests verify the conversion from ".in" to JSON. So if we convert all of them we should add a separate test for verifying the backward compatibility workflow.

[mrp089]

Oh, nice! I didn't realize the solver could already do that. Excellent! I think we should replace all .in with .json and leave 1-2 .in input files in a legacy folder.