SecurityPkg: PlatformPKProtectionLib: Added PK protection interface

SecurityPkg: PlatformPKProtectionLib: Added PK protection interface

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=3911

This patch provides an abstracted interface for platform to implement PK
variable related protection interface, which is designed to be used when
PK variable is about to be changed by UEFI firmware.

This change also provided a variable policy based library implementation
to accomodate platforms that supports variable policy for variable
protections.

Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Jian J Wang <jian.j.wang@intel.com>
Cc: Min Xu <min.m.xu@intel.com>
Signed-off-by: Kun Qin <kun.qin@microsoft.com>
Reviewed-by: Jiewen Yao <Jiewen.yao@intel.com>
Acked-by: Michael Kubacki <michael.kubacki@microsoft.com>