Enhance Shell 2.0 to not depend on keyboard driver implementation to fix the "CTRL+s" pause malfunction issue.

Signed-off-by: Ruiyu Ni <ruiyu.ni@intel.com>
Reviewed-by: Carsey Jaben <jaben.carsey@intel.com>

git-svn-id: svn://svn.code.sf.net/p/edk2/code/trunk/edk2/ShellPkg@15052 6f19259b-4bc3-4df7-8a09-765794883524