Add int return typehints to protected test helper methods

I made a part of the development.

@abarrio thanks for working on this. The scope should be limited to tests only, so in paths like core/tests/* and core/*/*/tests. We also don't want to add union types in this issue, to keep the scope down, so should be limited to int returns only.

Not sure why cspell is showing up but pipeline failed.

cspell was due to catch and I debugging some pipeline cache issues, let's move that to 🐛 Hardcode the core project ID for fetching artifacts from the gitlab API Needs review . Have reverted and rebased.

Nice, in that case change seems fine.