libyang MAINTENANCE cleanup header includes

Use iwyu tool and fix which headers are included
diff --git a/src/tree_schema_free.c b/src/tree_schema_free.c
index 09ce99d..f823cf7 100644
--- a/src/tree_schema_free.c
+++ b/src/tree_schema_free.c
@@ -16,6 +16,7 @@
 
 #include "common.h"
 #include "compat.h"
+#include "dict.h"
 #include "log.h"
 #include "plugins_exts.h"
 #include "plugins_types.h"