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.cpp

@@ -1,8 +1,12 @@
 #include <format>
 #include <chrono>
 #include <thread>
+#include <array>
+#include <string>
+#include <optional>
 #include <windows.h>
 
+#include "v0_cpp_imgui.h"
 #include "sdk/include/spicesdk.h"
 #include "sdk/include/spicesdk_io.h"
 
@@ -17,6 +21,24 @@ static spice_sdk_destroy_callback_func destroy_callback;
 static std::jthread worker_thread;
 static void worker_thread_main(std::stop_token stop_token);
 
+static std::optional<std::string> utf16_to_utf8(const wchar_t *text) {
+    const auto bytes = WideCharToMultiByte(
+        CP_UTF8, WC_ERR_INVALID_CHARS, text, -1, nullptr, 0, nullptr, nullptr);
+    if (bytes == 0) {
+        return std::nullopt;
+    }
+
+    std::string result(bytes, '\0');
+    if (WideCharToMultiByte(
+            CP_UTF8, WC_ERR_INVALID_CHARS, text, -1,
+            result.data(), bytes, nullptr, nullptr) != bytes) {
+        return std::nullopt;
+    }
+
+    result.pop_back();
+    return result;
+}
+
 // main entry point into the DLL
 // spice executable will call into this shortly after the game is partially 
 // initialized (but not quite fully booted just yet)
@@ -42,6 +64,37 @@ spice_sdk_entry_point(
 
     LOG_INFO("plugin loaded");
 
+    if (spice.get_plugin_directory) {
+        std::array<wchar_t, 32768> directory{};
+        uint32_t size = static_cast<uint32_t>(directory.size());
+        if (spice.get_plugin_directory(&spice, directory.data(), &size) ==
+            SPICE_SDK_STATUS_SUCCESS) {
+            if (const auto path = utf16_to_utf8(directory.data())) {
+                LOG_INFO(std::format("plugin directory: {}", *path).c_str());
+            }
+        }
+    }
+
+    if (spice.get_module_info) {
+        SPICE_SDK_MODULE_INFO info{};
+        info.size = sizeof(info);
+        if (spice.get_module_info(L"kernel32.dll", &info) == SPICE_SDK_STATUS_SUCCESS) {
+            LOG_INFO(std::format(
+                "kernel32 PE: {:x}_{:x}, base={:x}, size={:x}",
+                info.timestamp, info.entry_point, info.base, info.image_size).c_str());
+        }
+    }
+
+    if (spice.register_d3d9) {
+        status = sample_imgui::initialize(spice);
+        if (status != SPICE_SDK_STATUS_SUCCESS) {
+            LOG_INFO(std::format(
+                "D3D9 registration failed: {}", static_cast<int>(status)).c_str());
+        } else {
+            LOG_INFO("D3D9 renderer registered; Ctrl+Enter toggles the sample window");
+        }
+    }
+
     // spin up a worker thread
     worker_thread = std::jthread(worker_thread_main);
     return 1;
@@ -77,10 +130,18 @@ static ArrowButton arrow_buttons[] = {
 // worker thread for I/O
 static void worker_thread_main(std::stop_token stop_token) {
     bool coin_previous_state[10] = {};
+    bool window_toggle_previous_state = false;
     while (!stop_token.stop_requested()) {
 
-        // insert coin
         const bool control_pressed = (GetAsyncKeyState(VK_CONTROL) & 0x8000) != 0;
+        const bool window_toggle_pressed = control_pressed &&
+            ((GetAsyncKeyState(VK_RETURN) & 0x8000) != 0);
+        if (window_toggle_pressed && !window_toggle_previous_state) {
+            sample_imgui::toggle();
+        }
+        window_toggle_previous_state = window_toggle_pressed;
+
+        // insert coin
         for (uint8_t amount = 0; amount < 10; amount++) {
             const bool coin_pressed = control_pressed &&
                 ((GetAsyncKeyState('0' + amount) & 0x8000) != 0);