Move kotlin to it's own file

kapt is going to make kotlin a little more complicated, move the
rules and tests to their own files.

Bug: 122251693
Test: m checkbuild
Change-Id: Ieed78b97995ced210b710bd50c357514cc8e3bc6
diff --git a/Android.bp b/Android.bp
index 97f786e..2c400cf 100644
--- a/Android.bp
+++ b/Android.bp
@@ -248,6 +248,7 @@
         "java/java.go",
         "java/jdeps.go",
         "java/java_resources.go",
+        "java/kotlin.go",
         "java/prebuilt_apis.go",
         "java/proto.go",
         "java/sdk.go",
@@ -260,6 +261,7 @@
         "java/dexpreopt_test.go",
         "java/java_test.go",
         "java/jdeps_test.go",
+        "java/kotlin_test.go",
         "java/sdk_test.go",
     ],
     pluginFor: ["soong_build"],