Add java_genrule_combiner module

This module is intended to combine an implemenation generated by
java_genrule with headers from the rule's inputs.

Bug: b/285975842
Test: manual, TH
Change-Id: I9d83634ad7fa56fe5e0a6363d2891d34ac58257e
diff --git a/java/java.go b/java/java.go
index 900f0e3..fbd4d57 100644
--- a/java/java.go
+++ b/java/java.go
@@ -64,6 +64,7 @@
 	ctx.RegisterModuleType("java_api_library", ApiLibraryFactory)
 	ctx.RegisterModuleType("java_api_contribution", ApiContributionFactory)
 	ctx.RegisterModuleType("java_api_contribution_import", ApiContributionImportFactory)
+	ctx.RegisterModuleType("java_genrule_combiner", GenruleCombinerFactory)
 
 	// This mutator registers dependencies on dex2oat for modules that should be
 	// dexpreopted. This is done late when the final variants have been