LPS-34296 Export Import path methods refactoring

Hey Julio,

The purpose of this change is really straightforward - @KocsisDaniel did some refactoring on how we handle the path related methods during the staging.

Currently the PorletDataContext is used to generate paths required during the process, but as we introduced the StagedModelPathUtil our purpose was to have a centralized place where we can have all these methods.

The StagedModelPathUtil was originally called ExportImportPathUtil because it's purpose was to have all these path helper methods, Brian changed it to StagedModelPathUtil with saying if we need that to change in the future then we will.

Thanks,

Máté