Make the compare action label easier to understand when file names are identical

[Dominik-K]

If I've selected a file a.yaml for comparison in multi-root folder rootA and use the context-menu on another file b.yaml in root folder rootB, then showing "Compare with rootA/a.yaml", i.e. adding the root path rootA, instead of just a.yaml would be helpful.

cc #28344

[bpasero]

@Dominik-K well we actually never show any parent in that menu simply because we do not have much space. I think your suggestion applies already for single folder case too where you might want to know which file to compare to.

[Dominik-K]

@bpasero Oh, you're right. I didn't noticed this before as inside one project == folder, the filenames are mostly unique. But with the new, useful multi-root folders, it offers the opportunity to easily compare files with the same name, e.g. Kubernetes configurations, across different projects.

[bpasero]

Pushed changes for 2 things:

1. always show both file names in the compare action label

2. show enough context in case the filenames are identical (using the same algorithm we have when having the same file name opened multiple times