Replace C++/CLI components with P/Invoke components (#562)

* Replace C++/CLI components with P/Invoke

* Deleted C++/CLI projects

* Use Utf8StringHandle to marshal UTF-8 strings

* Use plaform-default calling convention

* Handle DLL preloading on Linux and macOS

* Change intermediate and output directories of native projects

* Improve P/Invoke documentation

Texture2DDecoderNative/bool32_t.h

@@ -0,0 +1,5 @@
+#pragma once
+
+#include <cstdint>
+
+typedef uint32_t bool32_t;