tree-wide: drop workarounds for statx()

struct statx in glibc header was introduced in glibc-2.28
(fd70af45528d59a00eb3190ef6706cb299488fcd), but at that time,
sys/stat.h conflicts with linux/stat.h. Since glibc-2.30
(5dad6ffbb2b76215cfcd38c3001778536ada8e8a), sys/stat.h includes
linux/stat.h if exists.

Since now our baseline of glibc is 2.31. Hence, we can drop workarounds
for struct statx by importing linux/stat.h from newer kernel (v6.14-rc4).

src/basic/missing_syscall.h

@@ -19,7 +19,6 @@
 #include "macro.h"
 #include "missing_keyctl.h"
 #include "missing_sched.h"
-#include "missing_stat.h"
 #include "missing_syscall_def.h"
 
 /* ======================================================================= */
@@ -223,28 +222,6 @@ static inline int missing_bpf(int cmd, union bpf_attr *attr, size_t size) {
 
 /* ======================================================================= */
 
-#if !HAVE_STATX
-struct statx;
-
-static inline ssize_t missing_statx(int dfd, const char *filename, unsigned flags, unsigned int mask, struct statx *buffer) {
-#  ifdef __NR_statx
-        return syscall(__NR_statx, dfd, filename, flags, mask, buffer);
-#  else
-        errno = ENOSYS;
-        return -1;
-#  endif
-}
-#endif
-
-/* This typedef is supposed to be always defined. */
-typedef struct statx struct_statx;
-
-#if !HAVE_STATX
-#  define statx(dfd, filename, flags, mask, buffer) missing_statx(dfd, filename, flags, mask, buffer)
-#endif
-
-/* ======================================================================= */
-
 #if !HAVE_SET_MEMPOLICY
 enum {
         MPOL_DEFAULT,