Co-authored by: supermilkdude67 <w.f.s.jazzfyre@gmail.com>

Add new setting to show/hide the Movie Window.

The `QtUtils::AdjustSizeWithinScreen()` function now centers the
widget on their parent window after the widget's size is adjusted. This
is required in some desktop environments (generally on Linux systems) to
ensure that the just-resized widget remains aligned with its parent
window.

The creation of the **Cheats Manager** dialog is now deferred to first
show, as creating it within the main window's constructor prevents the
dialog from knowing the real position of its parent window, which is
only properly calculated on first show.

For the same reasons, the analytics prompt is now shown only when the
application is ready (i.e. when the main window has been shown).

| Before | After |
| ------ | ----- |
| <img width="1920" height="1080" alt="[Dolphin Emulator] Misplaced analytics prompt" title="[Dolphin Emulator] Misplaced analytics prompt" src="https://github.com/user-attachments/assets/c3e43b3b-cf79-4398-b531-7de6068c583e" /> | <img width="1920" height="1080" alt="[Dolphin Emulator] Centered analytics prompt" title="[Dolphin Emulator] Centered analytics prompt" src="https://github.com/user-attachments/assets/a10d06d9-7438-4032-b96c-dfcb48826349" /> |
| <img width="1920" height="1080" alt="[Dolphin Emulator] Misplaced Settings dialog" title="[Dolphin Emulator] Misplaced Settings dialog" src="https://github.com/user-attachments/assets/f35b10ee-4f07-48d4-86f9-2537ad5ca7ca" /> | <img width="1920" height="1080" alt="[Dolphin Emulator] Centered Settings dialog" title="[Dolphin Emulator] Centered Settings dialog" src="https://github.com/user-attachments/assets/33e37237-77a4-44f6-a0e2-b709f65b672b" /> |
| <img width="1920" height="1080" alt="[Dolphin Emulator] Misplaced Cheats Manager dialog" title="[Dolphin Emulator] Misplaced Cheats Manager dialog" src="https://github.com/user-attachments/assets/1fbd3836-5639-4d5a-b57e-e2e21f21c9db" /> | <img width="1920" height="1080" alt="[Dolphin Emulator] Centered Cheats Manager dialog" title="[Dolphin Emulator] Centered Cheats Manager dialog" src="https://github.com/user-attachments/assets/3f2b1b50-de16-49b7-bac4-c444c6cab0bc" /> |

Make MainWindow::m_fifo_window a unique_ptr to ensure its destructor is
triggered when MainWindow is destroyed.

FIFOPlayerWindow doesn't set MainWindow as its parent in order to
prevent raising MainWindow when focusing FIFOPlayerWindow. This avoids
MainWindow covering up RenderWidget when, e.g., trying to use the object
range feature to pinpoint the index of a particular object.

As a consequence, unlike most QObjects FIFOPlayerWindow wasn't destroyed
when its parent widget was since it didn't have one.

Updates the Hardcore Changed callback to only signal EmulationStateChanged if the new Hardcore Mode setting is different from the previous one.

Core & UnitTests: Make overriding explicit and remove redundant virtual specifiers on overriding destructors