Add cpufreq=xen:hwp=off full system freezes workaround
Document the workaround for
https://github.com/QubesOS/qubes-issues/issues/8825 by setting the
corresponding Xen command-line parameter by editing the grub menu to be
able to boot into a non-frozen state, and then the grub config itself to
persist the workaround.
Move "Unable to reset PCI device" to Troubleshooting page
Despite it only affecting specific hardware, this seems like a better
place to document it when people run into it during installation.
The only change to the text itself is that the dom0 terminal instructions
now refer to the Qubes 4.2 way of opening it.
cpufreq=xen:hwp=off
full system freezes workaroundFixes #226.