xenpm: Add get-core-temp subcommand

get-core-temp allows querying the per-core CPU temperature and
per-package one on processors that supports Digital Temperature Sensors
(most Intel processors; as usual Dom0 drivers cannot work due to
misalignment between Dom0 vCPU and pCPUs).

Signed-off-by: Teddy Astie <teddy.astie@vates.tech>
Reviewed-by: Anthony PERARD <anthony.perard@vates.tech>
Acked-by: Oleksii Kurochko <oleksii.kurochko@gmail.com>

CHANGELOG.md

@@ -16,6 +16,8 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
      mitigate (by rate-limiting) the system wide impact of an HVM guest
      misusing atomic instructions.
    - Support for CPIO microcode in discrete multiboot modules.
+   - Introduce get-core-temp command to xenpm to query CPU temperatures on
+     Intel platforms.
 
  - On Arm:
    - Support for guest suspend and resume to/from RAM via vPSCI.