Merge META-INF/services/* files in merge_zips -jar

kotlinx_coroutines_test and kotlinx_coroutine_android each provide a
META-INF/services/kotlinx.coroutines.CoroutineExceptionHandler with
different contents, and the final contents needs to be the combination
of the two files.  Implement service merging in merge_zips when the
-jar argument is provided.

Bug: 290933559
Test: TestMergeZips
Change-Id: I69f80d1265c64c671d308ef4cdccfa1564abe056