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/hooks/graphics/backends/d3d9/d3d9_backend.cpp

@@ -22,6 +22,7 @@
 #include "launcher/shutdown.h"
 #include "misc/wintouchemu.h"
 #include "overlay/overlay.h"
+#include "sdk/d3d9.h"
 #include "util/detour.h"
 #include "util/deferlog.h"
 #include "util/flags_helper.h"
@@ -1511,6 +1512,8 @@ void graphics_d3d9_on_present(
         device->EndScene();
     }
 
+    sdk::d3d9::draw(hFocusWindow, device);
+
     // after the overlay render so the screenshot includes toasts / menus
     if (GRAPHICS_SCREENSHOT_INCLUDE_OVERLAY) {
         graphics_d3d9_process_screenshot(device, wrapped_device);