Bug#33306219 replace stdx::string_view by std::string_view

Issue
=====

stdx/string_view.h provided a C++17 equivalent of std::string_view for
C++14. Since C++17 is now the baseline, it can be removed.

Change
======

- replaced stdx::string_view by std::string_view
- removed mysql/harness/stdx/string_view.h

RB: 26943

Author: weigon

router/src/harness/include/mysql/harness/config_option.h

@@ -31,8 +31,8 @@
 #include <system_error>
 
 #include "mysql/harness/config_parser.h"
+#include "mysql/harness/stdx/attribute.h"  // STDX_NONNULL
 #include "mysql/harness/stdx/expected.h"
-#include "mysql/harness/stdx/string_view.h"
 
 namespace mysql_harness {
 enum class option_errc {
@@ -74,7 +74,7 @@ inline std::error_code make_error_code(option_errc e) noexcept {
 
 class ConfigOption {
  public:
-  ConfigOption(stdx::string_view name, stdx::string_view default_value)
+  ConfigOption(std::string_view name, std::string_view default_value)
       : name_{std::move(name)},
         is_required_{false},
         default_value_{std::move(default_value)} {
@@ -83,8 +83,8 @@ class ConfigOption {
     }
   }
 
-  explicit ConfigOption(::stdx::string_view name)
-      : name_{name}, is_required_{true} {
+  explicit ConfigOption(std::string_view name)
+      : name_{std::move(name)}, is_required_{true} {
     if (name.empty()) {
       throw std::invalid_argument("expected 'name' to be non-empty");
     }

router/src/harness/include/mysql/harness/net_ts/impl/netif.h

@@ -29,6 +29,7 @@
 #include <forward_list>
 #include <list>
 #include <string>
+#include <string_view>
 
 #if defined(__linux__) || defined(__FreeBSD__) || defined(__APPLE__) || \
     defined(__sun__)
@@ -55,7 +56,6 @@
 
 #include "mysql/harness/net_ts/internet.h"
 #include "mysql/harness/stdx/expected.h"
-#include "mysql/harness/stdx/string_view.h"
 
 namespace net {
 
@@ -331,7 +331,7 @@ class NetworkInterfaceResults {
 
 #elif defined(_WIN32)
   static stdx::expected<std::string, std::error_code> convert_wstring_to_utf8(
-      const stdx::wstring_view &ws) {
+      const std::wstring_view &ws) {
     std::string out;
 
     // first, call it with 0 to get the buffer length

router/src/harness/include/mysql/harness/net_ts/local.h

@@ -55,7 +55,6 @@
 #include "mysql/harness/net_ts/internet.h"
 #include "mysql/harness/net_ts/socket.h"
 #include "mysql/harness/stdx/expected.h"
-#include "mysql/harness/stdx/string_view.h"
 
 namespace local {
 
@@ -82,7 +81,7 @@ class basic_endpoint {
   // namespace' (starting with \0)
   //
   // note: can be 'constexpr' with C++2a's http://wg21.link/P0202 applied
-  basic_endpoint(stdx::string_view path) : data_{} {
+  basic_endpoint(std::string_view path) : data_{} {
     data_.sun_family = protocol_type().family();
 
     const auto truncated_path =