Add StrnSizeS() and AsciiStrnSizeS() APIs.
These 2 safe version APIs are used to replace StrSize() and
AsciiStrSize(). Those two APIs use similar checks as [Ascii]StrnLenS().
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Hao Wu <hao.a.wu@intel.com>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>