Refractor device image registration into function calls

Group the calls [here](https://github.com/intel/llvm/blob/cdf561a24705c6166c7aa05e0a09274dec121a7b/sycl/source/detail/program_manager/program_manager.cpp#L1187-L1228) into function instead of just wrapping them in a clause.

Each section that begins with `// ... and do sth` should be in its own function

Assignees: @sherry-yuan