RISC-V: extract reusable cache-types to cache utils

Part of RV-172

What

Groundwork for making the introduction of the block cache simpler:

• cache_layouts
• re-usability of Unparsed
• deleting an accidentally included old version of the block cache file (apologies).

Why

Moving more things out of instruction cache makes it simpler for the block cache to re-use them. Namely Unparsed for storing instructions, and the Sizes enum for controlling the size of the cache at compile time (allowing tests to run faster against the smaller cache size).

Having a general cache_layouts::Sizes also allows us to introduce the block cache without having to thread an extra generic parameter through various places.

Manually Testing

make -C src/riscv all

Benchmarking

Does not affect TPS on the benchmark machine

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.

/assign @ole.kruger
/assign @victor-dumitrescu
/assign @felix.puscasu1
/assign @anastasia.courtney
/assign @emturner

/assign_reviewer @ole.kruger
/assign_reviewer @victor-dumitrescu
/assign_reviewer @felix.puscasu1
/assign_reviewer @anastasia.courtney
/assign_reviewer @emturner

/unassign me
/unassign_reviewer me

/ready