clang-tidy: Fix all remaining misc-include-cleaner violations

- Remove unused includes
- Add common false positive headers to misc-include-cleaner.IgnoreHeaders
- Add IWYU pragma keep for uncommon false positive headers

src/mountfsd/mountfsd-manager.c

@@ -19,7 +19,6 @@
 #include "set.h"
 #include "signal-util.h"
 #include "socket-util.h"
-#include "stdio-util.h"
 #include "string-util.h"
 #include "time-util.h"
 #include "umask-util.h"