Packages: rename method original_build_info to last_build_info

🍀 Context

In #365828 (closed) we changed the method #original_build_info https://gitlab.com/gitlab-org/gitlab/-/blob/master/app/models/packages/package.rb#L293 to return the most recent pipeline.

🔥 Problem

Since now the method original_build_info returns the most recent pipeline, we should rename it to something like last_build_info to avoid any confusion.

🚒 Solution

Rename the method original_build_info to last_build_info and any references to it.