Move rules for building Android Mojo services to //mojo/android

examples/java_android/example_service/BUILD.gn

-import("//services/android/rules.gni")
+import("//mojo/android/rules.gni")
 
 group("example_service") {
   deps = [
     ":android_example_service",
   ]
 }
 
 mojo_android_java_application("android_example_service") {
   sources = [
     "src/org/chromium/examples/android/ExampleServiceApp.java",
   ]
 
   mojo_main = "org.chromium.examples.android.ExampleServiceApp"
 
   deps = [
     "//examples/apptest:bindings_java",
     "//mojo/public/interfaces/application:application_java",
     "//mojo/public/java:application",
   ]
 }