libyang MAINTENANCE cleanup header includes

Use iwyu tool and fix which headers are included
diff --git a/src/parser_xml.c b/src/parser_xml.c
index 8bed12f..f5bfc15 100644
--- a/src/parser_xml.c
+++ b/src/parser_xml.c
@@ -19,15 +19,17 @@
 
 #include "common.h"
 #include "context.h"
+#include "dict.h"
 #include "in_internal.h"
 #include "log.h"
 #include "parser_data.h"
 #include "parser_internal.h"
-#include "plugins_exts.h"
 #include "set.h"
+#include "tree.h"
 #include "tree_data.h"
 #include "tree_data_internal.h"
 #include "tree_schema.h"
+#include "tree_schema_internal.h"
 #include "validation.h"
 #include "xml.h"