Improve overlapping detection in ZFile.

ZFile now reports when files overlap in a zip. It previously
failed with a VerifyException and now, at least in cases where
the local header can still be read correctly (for example, a
file contained inside another file), it reports a nice error
that allows users to understand what the problem is.

Bug: 69835362
Change-Id: Ib34df31f97805f1d5ec9ba917dce7374ea6a7d22
Test: included