clang-tidy: Apply modernize-deprecated-headers

This can be reproduced according to the developer notes with something
like

( cd ./src/ && ../contrib/devtools/run-clang-tidy.py -p ../bld-cmake -fix -j $(nproc) )

Also, the header related changes were done manually.

src/test/fuzz/feeratediagram.cpp

@@ -2,7 +2,7 @@
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
-#include <stdint.h>
+#include <cstdint>
 
 #include <vector>
 
@@ -12,7 +12,7 @@
 #include <test/fuzz/fuzz.h>
 #include <test/fuzz/util.h>
 
-#include <assert.h>
+#include <cassert>
 
 namespace {