Update imgui to v1.90.9 (#7977)

third_party/imgui/misc/cpp/imgui_stdlib.cpp

@@ -1,16 +1,21 @@
 // dear imgui: wrappers for C++ standard library (STL) types (std::string, etc.)
 // This is also an example of how you may wrap your own similar types.
 
-// Compatibility:
-// - std::string support is only guaranteed to work from C++11.
-//   If you try to use it pre-C++11, please share your findings (w/ info about compiler/architecture)
-
 // Changelog:
 // - v0.10: Initial version. Added InputText() / InputTextMultiline() calls with std::string
 
+// See more C++ related extension (fmt, RAII, syntaxis sugar) on Wiki:
+//   https://github.com/ocornut/imgui/wiki/Useful-Extensions#cness
+
 #include "imgui.h"
 #include "imgui_stdlib.h"
 
+// Clang warnings with -Weverything
+#if defined(__clang__)
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wsign-conversion"    // warning: implicit conversion changes signedness
+#endif
+
 struct InputTextCallback_UserData
 {
     std::string*            Str;
@@ -74,3 +79,7 @@ bool ImGui::InputTextWithHint(const char* label, const char* hint, std::string*
     cb_user_data.ChainCallbackUserData = user_data;
     return InputTextWithHint(label, hint, (char*)str->c_str(), str->capacity() + 1, flags, InputTextCallback, &cb_user_data);
 }
+
+#if defined(__clang__)
+#pragma clang diagnostic pop
+#endif