rename ojluni's native/java_util_*.c -> native/*.c

These files had been renamed in commit 51b1b699
which was the commit that originally added them to AOSP. While they do
correspond to classes in java.util.zip, the fact that the files were renamed
makes it harder to identify the corresponding upstream file that they were
derived from.

This CL renames them back.

java_util_zip_ZipFile.h keeps the old name because that name is also
used by the (generated) file in upstream OpenJDK 8u121-b13.

Bug: 77572714
Test: Treehugger

Change-Id: I51387f7eb455b6124cc0938a18c683bf9ce8657b