MainWindow, Bugfix: Initialize geometries before calling GetWindowSystemInfo

[TryTwo]

https://bugs.dolphin-emu.org/issues/11191
https://bugs.dolphin-emu.org/issues/13355

On Windows:
InitControllers() -> GetWindowSystemInfo -> wsi.render_window being set will set/save the initial geometry, which will cause sizing bugs until it's set again by the user resizing/repositioning.

Not tested on other platforms. I don't see any problem with moving InitControllers() down, but someone should double check.

If the normal sized window is very small there will still be some issues with maximized windows restoring geometry, but that's more of a Qt bug.

[Tilka]

Works fine in gnome-shell. Side note: for a while now, Dolphin has had an irritating pop-in effect, at least on Linux. Not sure when it started. If you maximize Dolphin, close it, and reopen, it first gets drawn unmaximized, then quickly afterwards gets drawn maximized.

[TryTwo]

Thanks for testing! Would need to know generally when it broke, as I don't see any obvious changes. This PR changes code that has been there for a long time, rather than recent stuff.

[AdmiralCurtiss]

Seems fine.

[Owlet7]

This commit partially broke batch mode — Dolphin now initialises the GUI window when run with the -b / --batch command line arguments.

[CasualPokePlayer]

This commit also "breaks" dark mode on Windows slightly. Show() is the "proper" function to show the window, not show(), as Show() handles setting dark mode before actually showing the window (and also ends up checking for batch mode, like the later PR/code does). If you set dark mode after the window is visible (or unset it after setting it), it won't actually update the window title bar (until the user interacts with the app in some way that forces an update). This is due to windows hard caching the window theme, making it particularly annoying to update it programmatically (the simplest way to do so is to hide and reshow the window). With this change the window is shown before dark mode is set, therefore the user ends up seeing a mismatch (or at least sometimes, it appears to only be an issue if the system color mode is set to Light rather than Dark, and of course assuming the user set Dolphin's theme to Dark and not System for whatever reason)