src: do IWYU for some STL includes

Author: dsanders11

src/env.h

@@ -48,8 +48,11 @@
 #include <atomic>
 #include <cstdint>
 #include <functional>
-#include <iostream>
 #include <list>
+#include <memory>
+#include <ostream>
+#include <set>
+#include <string>
 #include <unordered_map>
 #include <unordered_set>
 #include <vector>

src/util.h

@@ -32,13 +32,14 @@
 #include <cstdlib>
 #include <cstring>
 
-#include <functional>  // std::function
+#include <array>
 #include <limits>
-#include <set>
+#include <memory>
 #include <string>
-#include <array>
+#include <type_traits>
 #include <unordered_map>
 #include <utility>
+#include <vector>
 
 #ifdef __GNUC__
 #define MUST_USE_RESULT __attribute__((warn_unused_result))