Expose ModuleType to Singletons

In order to implement some build statistics in Soong, expose the module
type (the string used to define the module) to singletons.

Change-Id: I441d12c7782bcf338b3654cfe907b8d2a7253594
diff --git a/singleton_ctx.go b/singleton_ctx.go
index e761e77..007e180 100644
--- a/singleton_ctx.go
+++ b/singleton_ctx.go
@@ -28,6 +28,7 @@
 	ModuleName(module Module) string
 	ModuleDir(module Module) string
 	ModuleSubDir(module Module) string
+	ModuleType(module Module) string
 	BlueprintFile(module Module) string
 
 	ModuleErrorf(module Module, format string, args ...interface{})
@@ -93,6 +94,10 @@
 	return s.context.ModuleSubDir(logicModule)
 }
 
+func (s *singletonContext) ModuleType(logicModule Module) string {
+	return s.context.ModuleType(logicModule)
+}
+
 func (s *singletonContext) BlueprintFile(logicModule Module) string {
 	return s.context.BlueprintFile(logicModule)
 }