Manual overloads for ImGui functions accepting text (#2319)

* wip2

* Implement AutoUtf8Buffer

* reformat

* Work on manual bindings

* restructure

* Name scripts properly

* Update utility functions to use ImU8String

* add overloads

* Add more overloads

* Use ImGuiWindow from gen, support AddCallback

* Use LibraryImport for custom ImGuiNative functinos

* Make manual overloads for string-returning functinos

* Make all overloads with self as its first parameter extension methods

* Fix overload resolution by removing unnecessary

* in => scoped in

* Fix compilation errors

imgui/Dalamud.Bindings.ImGui/Custom/ImGuiNative.Custom.cs

@@ -0,0 +1,40 @@
+using System.Numerics;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+
+namespace Dalamud.Bindings.ImGui;
+
+public static unsafe partial class ImGuiNative
+{
+    private const string LibraryName = "cimgui";
+
+    static ImGuiNative()
+    {
+        if (LibraryName != ImGui.GetLibraryName())
+        {
+            throw new(
+                $"{nameof(LibraryName)}(={LibraryName})" +
+                $" does not match " +
+                $"{nameof(ImGui)}.{nameof(ImGui.GetLibraryName)}(={ImGui.GetLibraryName()})");
+        }
+    }
+
+    [LibraryImport(LibraryName, EntryPoint = "ImDrawList_AddCallback")]
+    [UnmanagedCallConv(CallConvs = [typeof(CallConvCdecl)])]
+    public static partial void AddCallback(
+        ImDrawList* self,
+        delegate*<ImDrawList*, ImDrawCmd*, void> callback,
+        void* callbackData = null);
+
+    [LibraryImport(LibraryName, EntryPoint = "igInputTextEx")]
+    [UnmanagedCallConv(CallConvs = [typeof(CallConvCdecl)])]
+    public static partial int InputTextEx(
+        byte* label,
+        byte* hint,
+        byte* buf,
+        int bufSize,
+        Vector2 sizeArg,
+        ImGuiInputTextFlags flags = ImGuiInputTextFlags.None,
+        delegate* unmanaged[Cdecl]<ImGuiInputTextCallbackData*, int> callback = null,
+        void* userData = null);
+}