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/confidential-virt.c

@@ -9,9 +9,9 @@
 
 #include "confidential-virt.h"
 #include "confidential-virt-fundamental.h"
-#include "errno-util.h"
+#include "errno-util.h"                                 /* IWYU pragma: keep */
 #include "fd-util.h"
-#include "fileio.h"
+#include "fileio.h"                                     /* IWYU pragma: keep */
 #include "log.h"
 #include "string-table.h"
 #include "string-util.h"