RISC-V: Condense test framework of JIT and files in interpreter

Closes RV-525.

What

1. Condensing the test framework in jit.rs into generic Scenario instances.

2. Condensing the files in interpreter for run functions that are supported in the ICB.

Why

Currently the new files that have been creater in interpreter have been formed ad-hoc. We are converging where new run functions will live, which involves removing c.rs and i.rs and moving those functions to integer.rs. Please see JIT-Compilation 1 weekly meeting notes for plan of what files will exist going forward.

Also, the test framework in jit.rs involves a lot of repeated code. This MR condenses this by introducing the Scenario struct to add testing.

How

Manually Testing

make -C src/riscv all

Benchmarking

No visible impact on performance as this is just changing tests and moving functions to different files.

Tasks for the Author

• Link all Linear issues related to this MR using magic words (e.g. part of, relates to, closes).
• Eliminate dead code and other spurious artefacts introduced in your changes.
• Document new public functions, methods and types.
• Make sure the documentation for updated functions, methods, and types is correct.
• Add tests for bugs that have been fixed.
• Put in reasonable effort to ensure that CI will pass.
  • make -C src/riscv
  • dune build src/lib_riscv
  • dune build src/rust_deps
• Benchmark performance and populate the table above if needed.
• Explain changes to regression test captures when applicable.
• Write commit messages to reflect the changes they're about.
• Self-review your changes to ensure they are high-quality.
• Complete all of the above before assigning this MR to reviewers.