RISC-V: rename dummy PVM to node PVM

Victor Dumitrescurequested to merge
vdum@riscv_rename_dummy_pvm into master

What

A simple rename MR

Why

The DummyPvm type started as a Rust reimplementation of the RISC-V dummy PVM to be used in the rollup node and has since been the basis of the actual PVM.

Merge request reports