Fix the issue that changing merge_annotations_dir doesn't trigger build

We don't have API exported to glob any dir outside of current module.
Any files deps outside of current module should be either a
filegroup/filegroup or a customized module.

We already have similar customized module to track droiddoc-template, so
rename it to be more generic so that it can be used by
merge_annotations_dir also.

Bug: b/111916275, b/70351683
Test: touch manual/android/support/design/widget/annotations.xml, and m
-j metalava-api-stubs-docs, and check the built output srcjar.

Change-Id: I75420ddba69785e46bea75b6dd3f189be7cfe5ad
diff --git a/java/java_test.go b/java/java_test.go
index 6bba29b..434bcc7 100644
--- a/java/java_test.go
+++ b/java/java_test.go
@@ -84,7 +84,7 @@
 	ctx.RegisterModuleType("genrule", android.ModuleFactoryAdaptor(genrule.GenRuleFactory))
 	ctx.RegisterModuleType("droiddoc", android.ModuleFactoryAdaptor(DroiddocFactory))
 	ctx.RegisterModuleType("droiddoc_host", android.ModuleFactoryAdaptor(DroiddocHostFactory))
-	ctx.RegisterModuleType("droiddoc_template", android.ModuleFactoryAdaptor(DroiddocTemplateFactory))
+	ctx.RegisterModuleType("droiddoc_template", android.ModuleFactoryAdaptor(ExportedDroiddocDirFactory))
 	ctx.RegisterModuleType("java_sdk_library", android.ModuleFactoryAdaptor(sdkLibraryFactory))
 	ctx.RegisterModuleType("prebuilt_apis", android.ModuleFactoryAdaptor(prebuiltApisFactory))
 	ctx.PreArchMutators(android.RegisterPrebuiltsPreArchMutators)