Multiple "scenes" for screen resize (#270)

## Link to GitHub Issue, if one exists
Fixes #263 

## Description of change
Add "scenes" to screen resize.

* UI changes - F11 menu now has a "scene switcher" for `Scene 1/2/3/4`.
Clean up other UI bits.
* Add hotkeys for `Screen Resize Scene 1`, `Screen Resize 2`, and so on.
* Detect hot key and trigger resizes.
* Add additional objects to screen_resize.json for saving and loading
the new scene settings.
* Existing screen resize data is backwards compatible (can be
loaded/saved to JSON), and is treated as `Scene 1`.
* Add API endpoint for `Resize`, allow toggling resize on/off, switching
active scene
* Add Python wrapper. Did not bother with the other wrappers (Dart, C++,
etc)...

## Compiling
🥇 

## Testing
Still testing, but seems to work fine for TDJ.

src/spice2x/api/modules/resize.cpp

@@ -0,0 +1,53 @@
+#include "resize.h"
+#include "external/rapidjson/document.h"
+#include "cfg/screen_resize.h"
+
+using namespace std::placeholders;
+using namespace rapidjson;
+
+namespace api::modules {
+
+    static thread_local std::vector<uint8_t> CAPTURE_BUFFER;
+
+    Resize::Resize() : Module("resize") {
+        functions["image_resize_enable"] = std::bind(&Resize::image_resize_enable, this, _1, _2);
+        functions["image_resize_set_scene"] = std::bind(&Resize::image_resize_set_scene, this, _1, _2);
+    }
+
+    /**
+     * image_resize_enable(enable: bool)
+     */
+    void Resize::image_resize_enable(Request &req, Response &res) {
+        if (req.params.Size() < 1) {
+            return error_params_insufficient(res);
+        }
+        if (!req.params[0].IsBool()) {
+            return error_type(res, "enable", "bool");
+        }
+
+        cfg::SCREENRESIZE->enable_screen_resize = req.params[0].GetBool();
+    }
+
+    /**
+     * image_resize_set_scene(scene: int)
+     */
+    void Resize::image_resize_set_scene(Request &req, Response &res) {
+        if (req.params.Size() < 1) {
+            return error_params_insufficient(res);
+        }
+        if (!req.params[0].IsInt()) {
+            return error_type(res, "scene", "int");
+        }
+
+        const auto scene = req.params[0].GetInt();
+        if (scene < 0 || (int)std::size(cfg::SCREENRESIZE->scene_settings) < scene) {
+            return error(res, "invalid scene number");
+        }
+        if (scene == 0) {
+            cfg::SCREENRESIZE->enable_screen_resize = false;
+        } else {
+            cfg::SCREENRESIZE->enable_screen_resize = true;
+            cfg::SCREENRESIZE->screen_resize_current_scene = scene - 1;
+        }
+    }
+}

src/spice2x/api/modules/resize.h

@@ -0,0 +1,18 @@
+#pragma once
+
+#include "api/module.h"
+#include "api/request.h"
+
+namespace api::modules {
+
+    class Resize : public Module {
+    public:
+        Resize();
+
+    private:
+
+        // function definitions
+        void image_resize_enable(Request &req, Response &res);
+        void image_resize_set_scene(Request &req, Response &res);
+    };
+}