Merge utility functions of search and parser
Currently, search/utils and rddl_parser/utils are nearly identical. A change to one utility function in search often requires copy/pasting the entire file to the parser. Furthermore, while a new implementation could work in search, there could be issues in the parser, that are only noticed after the file was copied, making a lot of extra work.
I propose to merge the utility classes to one location, e.g. src/utils.