Remove redundant test path that is shared across all tests

[Tyriar]

Testing #119545

Creating an issue from #119545 (comment)

The selfhost provider publishes tests using their full file path. This is rather ugly, not sure if/what solution I will use to fix this.

Perhaps the common parts of the path should be removed, leaving enough to identify them uniquely, similar to how tab disambiguation works:

For VS Code this would let us remove src/vs I think