BaseTools: Follow PI1.4a to fix artificial limitation of PCD SkuId range

BaseTools: Follow PI1.4a to fix artificial limitation of PCD SkuId range

Current BaseTools follow previous PI spec to use UINT8 for SkuId, to
follow PI1.4a, BaseTools need to be updated to fix artificial limitation
of PCD SkuId range.

This patch is to update BaseTools to use UINT64 for SkuId, since the
PCD database structure needs to be naturally aligned, the PCD database
structure layout is adjusted to keep the natural alignment and version
is updated to 6.

Note: As the PCD database structure layout is adjusted, the structure
definition in MdeModulePkg/Include/Guid/PcdDataBaseSignatureGuid.h and
PCD drivers also need to be updated. That means the source code and
BaseTools need to be upgraded at the same time, and if they are not
upgraded at the same time, build error like below will be triggered
to help user identify the problem.

"Please make sure the version of PCD PEIM Service and the generated
PCD PEI Database match."

Cc: Liming Gao <liming.gao@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Yonghong Zhu <yonghong.zhu@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>