Avoid duplicate checking of trailing slash in ZipFile.getZipEntry

ZipFile.getZipEntry currently includes logic to check if a CEN entry looked up as "name" returned a match for "name/" with a trailing slash. Similar logic is already done in the ZipFile.Source.getEntryPos method, but this method only returns the CEN position, not the resolved directory name.

By changing ZipFile.Source.getEntryPos to return both the CEN position and the resolved name, we can remove this logic from ZipFile.getZipEntry.