Include <optional> in headers that use std::optional (#10044)

Detected when compiling with gcc-11 where <optional> wasn't being brought in by other standard headers

Authors:
  - Robert Maynard (https://github.com/robertmaynard)

Approvers:
  - Bradley Dice (https://github.com/bdice)
  - David Wendt (https://github.com/davidwendt)
  - Nghia Truong (https://github.com/ttnghia)
  - Vyas Ramasubramani (https://github.com/vyasr)

URL: #10044

cpp/benchmarks/common/generate_benchmark_input.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2020-2021, NVIDIA CORPORATION.
+ * Copyright (c) 2020-2022, NVIDIA CORPORATION.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -31,6 +31,7 @@
 
 #include <future>
 #include <memory>
+#include <optional>
 #include <random>
 #include <thread>
 #include <vector>

cpp/include/cudf/strings/repeat_strings.hpp

@@ -18,6 +18,8 @@
 #include <cudf/scalar/scalar.hpp>
 #include <cudf/strings/strings_column_view.hpp>
 
+#include <optional>
+
 namespace cudf {
 namespace strings {
 /**

cpp/include/cudf/strings/replace_re.hpp

@@ -20,6 +20,8 @@
 #include <cudf/strings/regex/flags.hpp>
 #include <cudf/strings/strings_column_view.hpp>
 
+#include <optional>
+
 namespace cudf {
 namespace strings {
 /**

cpp/src/io/utilities/trie.cuh

@@ -23,6 +23,8 @@
 
 #include <cudf/utilities/span.hpp>
 
+#include <optional>
+
 namespace cudf {
 namespace detail {
 static constexpr char trie_terminating_character = '\n';