LibGUI+Everywhere: Use fallible Window::set_main_widget() everywhere :^)

Rip that bandaid off!

This does the following, in one big, awkward jump:
- Replace all uses of `set_main_widget<Foo>()` with the `try` version.
- Remove `set_main_widget<Foo>()`.
- Rename the `try` version to just be `set_main_widget` because it's now
  the only one.

The majority of places that call `set_main_widget<Foo>()` are inside
constructors, so this unfortunately gives us a big batch of new
`release_value_but_fixme_should_propagate_errors()` calls.

2 files changed, 6 insertions, 6 deletions

diff --git a/Userland/Games/Chess/PromotionDialog.cpp b/Userland/Games/Chess/PromotionDialog.cpp
index f20ab09148..06e742ae24 100644
--- a/Userland/Games/Chess/PromotionDialog.cpp
+++ b/Userland/Games/Chess/PromotionDialog.cpp
@@ -17,13 +17,13 @@ PromotionDialog::PromotionDialog(ChessWidget& chess_widget)
     set_icon(chess_widget.window()->icon());
     resize(70 * 4, 70);
 
-    auto& main_widget = set_main_widget<GUI::Frame>();
-    main_widget.set_frame_shape(Gfx::FrameShape::Container);
-    main_widget.set_fill_with_background_color(true);
-    main_widget.set_layout<GUI::HorizontalBoxLayout>();
+    auto main_widget = set_main_widget<GUI::Frame>().release_value_but_fixme_should_propagate_errors();
+    main_widget->set_frame_shape(Gfx::FrameShape::Container);
+    main_widget->set_fill_with_background_color(true);
+    main_widget->set_layout<GUI::HorizontalBoxLayout>();
 
     for (auto const& type : { Chess::Type::Queen, Chess::Type::Knight, Chess::Type::Rook, Chess::Type::Bishop }) {
-        auto& button = main_widget.add<GUI::Button>("");
+        auto& button = main_widget->add<GUI::Button>("");
         button.set_fixed_height(70);
         button.set_icon(chess_widget.get_piece_graphic({ chess_widget.board().turn(), type }));
         button.on_click = [this, type](auto) {
diff --git a/Userland/Games/Chess/main.cpp b/Userland/Games/Chess/main.cpp
index 5dfa1145fd..8e40931ec3 100644
--- a/Userland/Games/Chess/main.cpp
+++ b/Userland/Games/Chess/main.cpp
@@ -34,7 +34,7 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
     auto app_icon = TRY(GUI::Icon::try_create_default_icon("app-chess"sv));
 
     auto window = TRY(GUI::Window::try_create());
-    auto widget = TRY(window->try_set_main_widget<ChessWidget>());
+    auto widget = TRY(window->set_main_widget<ChessWidget>());
 
     TRY(Core::System::unveil("/sys/kernel/processes", "r"));
     TRY(Core::System::unveil("/res", "r"));