LPS-44476 SearchResultUtil: introduce tests to document current behavior

Hi @sergiogonzalez!

This is the first in a series of small PRs for the **Search** subsystem. This one contains only the `SearchResultUtil` characterization tests, to get that going. As soon as it gets on master, I'll follow with more chunks breaking up the [intended refactoring](https://github.com/sergiogonzalez/liferay-portal/pull/1440) in logical parts.

Already incorporates review contributions from @marcellustavares.

@rotty3000 Even though this PR has only tests, with no actual refactorings yet, your insights are welcome as always.