Change "resize to fit" shortcut to RCtrl+w

For convenience, RCtrl+x (and Cmd+x) will be used for "cut text to
clipboard", in addition to LCtrl+x.

app/src/cli.c

@@ -196,7 +196,7 @@ scrcpy_print_usage(const char *arg0) {
         "    RCtrl+g\n"
         "        Resize window to 1:1 (pixel-perfect)\n"
         "\n"
-        "    RCtrl+x\n"
+        "    RCtrl+w\n"
         "    Double-click on black borders\n"
         "        Resize window to remove black borders\n"
         "\n"

app/src/input_manager.c

@@ -355,7 +355,7 @@ input_manager_process_key(struct input_manager *im,
                     screen_switch_fullscreen(im->screen);
                 }
                 return;
-            case SDLK_x:
+            case SDLK_w:
                 if (!shift && !repeat && down) {
                     screen_resize_to_fit(im->screen);
                 }