Make apex.ApexBundleFactory public

Art needs to be able to create an ApexBundle with a LoadHook to
support art testing using the HOST_PREFER_32_BIT=true hack.

Bug: 120617876
Test: HOST_PREFER_32_BIT=true m nothing
Change-Id: Ia11e61a92094dfbc013c6c53a6edff33371ed8e1
diff --git a/apex/apex_test.go b/apex/apex_test.go
index d1794ee..b178829 100644
--- a/apex/apex_test.go
+++ b/apex/apex_test.go
@@ -28,7 +28,7 @@
 	defer teardown(buildDir)
 
 	ctx := android.NewTestArchContext()
-	ctx.RegisterModuleType("apex", android.ModuleFactoryAdaptor(apexBundleFactory))
+	ctx.RegisterModuleType("apex", android.ModuleFactoryAdaptor(ApexBundleFactory))
 	ctx.RegisterModuleType("apex_key", android.ModuleFactoryAdaptor(apexKeyFactory))
 
 	ctx.PostDepsMutators(func(ctx android.RegisterMutatorsContext) {