Adding back the HWLoop

Created by: davideschiavone

This PR has the HIGHEST priority according to the Core Task Group Plan

• The HWLoop has been added back to the core

• It moves the RVC decoder from the IF to the ID stage

• It uses a new prefetcher

It has major changes, so before merging:

• 2 or more users should check the synthesis results in TIMING and AREA

• The CI check in core-v-verif should not be broken

In the PULP team, we already checked the synthesis. Functional bugs not yet. I ask @Silabs-ArjanB to carefully review the PR and check at least the synthesis Adding @MikeOpenHWGroup for the sanity check on core-v-verif

A new hwlp test has been added. However, it is here only temporanely as it must be moved to core-v-verif (together with the interrupt test)