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/launcher/launcher.cpp

@@ -2908,7 +2908,7 @@ int main_implementation(int argc, char *argv[]) {
         bt5api_dispose();
     }
 
-    sdk::fini_sdk_modules();
+    sdk::fini_sdk_modules(true);
 
     // stop raw input
     hotkeys::disable_raw_input();