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/basic/alloc-util.h

@@ -4,7 +4,7 @@
 #include <stdlib.h>
 
 #include "basic-forward.h"
-#include "memory-util.h"
+#include "memory-util.h"        /* IWYU pragma: keep */
 
 #if HAS_FEATURE_MEMORY_SANITIZER
 #  include <sanitizer/msan_interface.h>