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

jar/Android.bp

@@ -21,6 +21,7 @@ bootstrap_go_package {
     pkgPath: "android/soong/jar",
     srcs: [
         "jar.go",
+        "services.go",
     ],
     testSrcs: [
         "jar_test.go",