The tenmplated function getSingleOpOfType was duplicated in two files.
This function is generic enough that other conversion/anaylsis might use it. In
order to avoid more copy/paste of this function, this patch move it into a new
header files for utility function working on Blocks.
https://llvm.discourse.group/t/where-to-move-utility-function/4330
Please don't do using namespace in a header.