RISC-V: Delete read/write_some functions from Manager traits

Part of RV-288

What

Deletes dead code no longer used, namely read_some & write_some from ManagerRead & ManagerWrite traits respectively.

Why

Will make things easier when implementing other backends like the proof generating, verification, refutation backends.

Manually Testing

make -C src/riscv all

Benchmarking

Interpreter performance not impacted

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.
• Benchmark performance and populate the table above if needed.
• 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.