Minor updates

[lobis]

In this PR I introduce small changes motivated by other PRs.

• Using std::filesystem::weakly_canonical to save the output file path inside TRestRun after "forming". Saving the path as a canonical absolute path helps solve a bug showing the wrong path at the end of simulation when launching from the IDE. Currently paths are being stored with things such as "./", these things are now resolved before storing and the path is absolute.
• TRestHits no longer inherits from TObject as this is not necessary unless we want to store the hits directly in the root file, but we always save the class containing the hits, such as a TRestEvent. This reduces the members of the class which reduces the visual clutter when using the root explorer. Also TRestHits::RemoveHits is now virtual so it can be overriden in other classes.
• All data members of TRestHits such as fNHits have been made protected instead of public and should be accessed by the corresponding getter which already existed before this PR.

Related PR:

• Update required from framework/TRestHits detectorlib#55
• Fix compilation problem after making TRestHits members protected tracklib#21
• Minor updates connectorslib#18