sdk: add get_module_info, get_plugin_directory, d3d9 callbacks (#908)

## Link to GitHub Issue or related Pull Request, if one exists
n/a

## Description of change
To make plugin development easier, add `get_module_info` and
`get_plugin_directory` to deal with common tasks for hooking DLLs and
reading INI files.

Also, add the ability to register for d3d9 present callbacks via
`register_d3d9`, which makes it significantly easier for plugins to draw
things on screen.

## Testing
See sample code.

src/spice2x/sdk/sample/v0/cpp/v0_cpp_imgui.h

@@ -0,0 +1,10 @@
+#pragma once
+
+#include "sdk/include/spicesdk.h"
+
+namespace sample_imgui {
+
+SPICE_SDK_STATUS_CODE initialize(const SPICE_SDK_V0 &spice);
+void toggle();
+
+}