BaseTools: Add PCDs conditional operator function

BaseTools: Add PCDs conditional operator function

Parse PCDS value like A >B ? C :D
if A > B is True, the result is C, else the result is D

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