Add missing headers in FixedVector and Span

core/templates/fixed_vector.h

@@ -30,6 +30,8 @@
 
 #pragma once
 
+#include "core/templates/span.h"
+
 /**
  * A high performance Vector of fixed capacity.
  * Especially useful if you need to create an array on the stack, to

core/templates/span.h

@@ -30,6 +30,7 @@
 
 #pragma once
 
+#include "core/error/error_macros.h"
 #include "core/typedefs.h"
 
 // Equivalent of std::span.