Convert checkApexAvailability to use ModuleProxy.

Bug: 377723687
Test: Unit tests and compare the ninja and mk files generated.
Change-Id: I7582db8e22e94d0a9db7715a76bb6ed34c166a4e
diff --git a/android/module_proxy.go b/android/module_proxy.go
index 30459b9..8cc8fa1 100644
--- a/android/module_proxy.go
+++ b/android/module_proxy.go
@@ -189,7 +189,7 @@
 }
 
 func (m ModuleProxy) String() string {
-	return m.module.Name()
+	return m.module.String()
 }
 
 func (m ModuleProxy) qualifiedModuleId(ctx BaseModuleContext) qualifiedModuleName {