Remove unused java testing methods

Also, stops exporting methods that are no longer used outside the java
package.

Bug: 181070625
Test: m nothing
Change-Id: I23d35bbc21f82f2dae802aa53badda4c58b41024
diff --git a/java/java.go b/java/java.go
index 9786947..70ad879 100644
--- a/java/java.go
+++ b/java/java.go
@@ -33,12 +33,12 @@
 )
 
 func init() {
-	RegisterJavaBuildComponents(android.InitRegistrationContext)
+	registerJavaBuildComponents(android.InitRegistrationContext)
 
 	RegisterJavaSdkMemberTypes()
 }
 
-func RegisterJavaBuildComponents(ctx android.RegistrationContext) {
+func registerJavaBuildComponents(ctx android.RegistrationContext) {
 	ctx.RegisterModuleType("java_defaults", DefaultsFactory)
 
 	ctx.RegisterModuleType("java_library", LibraryFactory)