MdeModulePkg/Browser: Enhance the logic when getting value from AltResp

MdeModulePkg/Browser: Enhance the logic when getting value from AltResp

This patch is to enhance SetupBrowser to handle following two cases:
1. When searching BlockName in AltResp, the hex digits of related BlockName
   in AltResp may be in uppercase.
2. When converting the Value in AltResp to HiiValue, the length of value
   string is bigger than the length of StorageWidth of the question.

Cc: Liming Gao <liming.gao@intel.com>
Cc: Eric Dong <eric.dong@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Dandan Bi <dandan.bi@intel.com>
Reviewed-by: Eric Dong <eric.dong@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>