Define method and properties for phosphor-post-code-manager

1. Method: std::vector<uint64_t> PostCode::getPostCodes(uint16_t index)
2. Properties: CurrentBootCycleIndex/MaxBootCycleNum

Tested:
    Every cycle post codes is saved in "/var/lib/phosphor-post-code-manager"
    "1" file is saved all post codes for cycle 1
    "2" file is saved all post codes for cycle 2
    "CurrentBootCycleIndex" file is saved the current boot cycle number.
    root@wolfpass:/var/lib/phosphor-post-code-manager# ls
      1  2 CurrentBootCycleIndex
Implementation is at:
https://gerrit.openbmc-project.xyz/c/openbmc/phosphor-post-code-manager/+/18503

Change-Id: Iaca6042192771fe347cabcccd3d074fd9eb2926e
Signed-off-by: Kuiying Wang <kuiying.wang@intel.com>
1 file changed