Add package C-state Demotion/Undemotion support

[yump]

My Arrow Lake platform provides the following 4 knobs in BIOS:

1. C-state Auto Demotion, possible values are: C1, Disabled
2. C-state Un-demotion, possible values are: C1, Disabled
3. Package C-state Demotion, possible values are: Enabled, Disabled
4. Package C-state Undemotion, possible values are: Enabled, Disabled

The "pepc cstates" conveniently provides explanation for #1 and #2, along with command line options to read and modify #1 and #2.

Please, add similar support for #3 and #4: explanation + options to read and modify.