bmcweb: share processor inventory interfaces

Move the common processor D-Bus interface list into
processor_utils.hpp and use it for processor, chassis, PCIe, and
environment metrics. This avoids duplicate lists drifting apart.

Tested: Only code extraction. Verified Processor responses are
unchanged.

Change-Id: I952c9985c393a903d2949dc3c7b5b592381e4b7f
Signed-off-by: Jacky Huang <jackyhuang@nvidia.com>