[VCM] Fix issues on certain systems (#12481)

- Don't depend on System.Windows.Forms in the Settings -> use callback instead
- Fix overlay image setting saving
- Use dynamic DLL loading in Interop
- Load VCM only when mf.dll is available

src/modules/videoconference/VideoConferenceShared/DLLProviderHelpers.h

@@ -0,0 +1,33 @@
+#pragma once
+
+#define WIN32_LEAN_AND_MEAN
+#include <Windows.h>
+
+#include <optional>
+#include <functional>
+#include <type_traits>
+
+#define DECLARE_DLL_FUNCTION(NAME) \
+    std::function<decltype(::NAME)> NAME = (std::add_pointer_t<decltype(::NAME)>)GetProcAddress(_library_handle, #NAME);
+
+#define DECLARE_DLL_PROVIDER_BEGIN(DLL_NAME)                       \
+    class DLL_NAME##APIProvider final                              \
+    {                                                              \
+        HMODULE _library_handle;                                   \
+        DLL_NAME##APIProvider(HMODULE h) : _library_handle{ h } {} \
+                                                                   \
+    public:                                                        \
+        ~DLL_NAME##APIProvider() { FreeLibrary(_library_handle); } \
+        static std::optional<DLL_NAME##APIProvider> create()       \
+        {                                                          \
+            HMODULE h = LoadLibraryA(#DLL_NAME ".dll");            \
+            std::optional<DLL_NAME##APIProvider> result;           \
+            if (!h)                                                \
+                return result;                                     \
+            result.emplace(DLL_NAME##APIProvider{ h });            \
+            return result;                                         \
+        }
+
+#define DECLAR_DLL_PROVIDER_END \
+    }                           \
+    ;