Remove STL includes for files without std:: symbols

-- convert some <cstddef> to <stddef.h> for compliance.
-- fix one IWYU

Change-Id: I785da3e836ad06943fe32fd074e4db4291a04e37
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/85271
Auto-Submit: Tom Sepez <tsepez@chromium.org>
Commit-Queue: Tom Sepez <tsepez@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
diff --git a/testing/fuzzers/pdf_streamparser_fuzzer.cc b/testing/fuzzers/pdf_streamparser_fuzzer.cc
index 1d1144b..68506d8 100644
--- a/testing/fuzzers/pdf_streamparser_fuzzer.cc
+++ b/testing/fuzzers/pdf_streamparser_fuzzer.cc
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include <cstdint>
+#include <stdint.h>
 
 #include "core/fpdfapi/page/cpdf_streamparser.h"
 #include "core/fpdfapi/parser/cpdf_object.h"