BaseTools/Pkcs7Sign: Add PKCS7 test key include files

BaseTools/Pkcs7Sign: Add PKCS7 test key include files

https://bugzilla.tianocore.org/show_bug.cgi?id=1073

Add PCD statement include files for the PKCS7 test key.
* gEfiSecurityPkgTokenSpaceGuid.PcdPkcs7CertBuffer
* gFmpDevicePkgTokenSpaceGuid.PcdFmpDevicePkcs7CertBufferXdr

These include files can be used in !include statements in PCD
sections of a platform DSC file to assign these PCDs to the
test key certificate values.

Cc: Yonghong Zhu <yonghong.zhu@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Michael D Kinney <michael.d.kinney@intel.com>
Reviewed-by: Yonghong Zhu <yonghong.zhu@intel.com>