basic + fundamental: Clean up includes

Split out of #37344.

src/basic/errno-list.h

@@ -1,30 +1,11 @@
 /* SPDX-License-Identifier: LGPL-2.1-or-later */
 #pragma once
 
-#include <errno.h>
-#include <stdbool.h>
-#include <string.h>
+#include "forward.h"
 
-#include "macro.h"
-
-/*
- * MAX_ERRNO is defined as 4095 in linux/err.h
- * We use the same value here.
- */
-#define ERRNO_MAX 4095
-
-#if HAVE_STRERRORNAME_NP
-static inline const char* errno_to_name(int id) {
-        if (id == 0) /* To stay in line with our own impl */
-                return NULL;
-
-        return strerrorname_np(ABS(id));
-}
-#else
 const char* errno_to_name(int id);
-#endif
 
-int errno_from_name(const char *name);
+int errno_from_name(const char *name) _const_;
 
 static inline bool errno_is_valid(int n) {
         return n > 0 && n <= ERRNO_MAX;