findByPath: handle files clashing by path

[odeke-em]

This PR is a work in progress (not complete) to fix up a couple of bugs that were caused due to the design remote findBy* functions with local filesystem inherent behaviour for a remote that allows path duplication e.g
FindByPath(...) previously returned a single file
However
FindByPath(...) actually picked the first path presented to it because Google Drive can allow for different files to have the same relative path, with no problem but the local file system will not.

With the new behaviour, a FindByPath call should return all found files.

This kind of old behaviour causes issues like not all the clashes being listed, not fully urlifying nor opening files, not properling list-ing, stat-ing and many others.

[odeke-em]

Closing in favor of more superior PR #528