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.

1 files changed, 1 insertions, 1 deletions

diff --git a/Userland/Demos/Screensaver/main.cpp b/Userland/Demos/Screensaver/main.cpp
index 53eca2a247..5a549976de 100644
--- a/Userland/Demos/Screensaver/main.cpp
+++ b/Userland/Demos/Screensaver/main.cpp
@@ -86,7 +86,7 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
     TRY(help_menu->try_add_action(GUI::CommonActions::make_command_palette_action(window)));
     TRY(help_menu->try_add_action(GUI::CommonActions::make_about_action("Screensaver", app_icon, window)));
 
-    auto main_widget = TRY(window->try_set_main_widget<GUI::Widget>());
+    auto main_widget = TRY(window->set_main_widget<GUI::Widget>());
     main_widget->set_fill_with_background_color(true);
     main_widget->set_layout<GUI::VerticalBoxLayout>();