Updated user manual to address several configuration (second pass) (!1696) · Merge requests · OpenHW Group / backup-20241120 / cva6

Created by: jquevremont

This PR is in addition to the "first pass" (PR https://github.com/openhwgroup/cva6/pull/1685).

It includes:

Minor update of Core_Integration.rst (looking for contributors)
Applicability of CSR_Performance_Counters to configurations
RISCV_Instructions.rst split into as many files as RISC-V extensions with their applicability to configurations (to ease the future generation of user manuals dedicated to each configuration).

What will need updates after first and second passes are merged:

PMP.rst (when their presence/absence in CV32E6?X is confirmed)
Traps_Interrupts_Exceptions.rst: expected significant impact of machine-only CV32E6?X (will need a contribution from @JeanRochCoulon's team)

Updated user manual to address several configuration (second pass)