[electron] Splash screen behavior is inconsistent with regards to starting maximized/unmaximized

[tortmayr]

Bug Description:

When a splash screen is configured by default the preventAutomaticShow option is set to true.
This means the main window should remain invisible until the layout is fully initialized.
This works as expected when the Theia electron app starts the main Window unmaximized.
However, when the app is started with isMaximized=true then the main Window will still show early.
Resulting in an overlay of the preload window and the splash screen

Expected behavior:
Using a splashscreen, the main window should remain invisible until the splash screen is closed independent of whether the window is maximized or not

Steps to Reproduce:

1. Build the electron example app
2. Start the app
3. If the window starts not maximized:
   (State. Splash screen is shown, main window is invisible until splash screen is removed)
   3.1 Maximize the window
   3.2 Close the app
   3.3 Restart the app and continue with 4.
4. If the window is maximized
   State: Splash screen is shown. Main window becomes immediately visible and is visible alongside splashscreen

Here is demonstration of the Bug using Theia IDE under Linux:

theia_splash.mp4

Additional Information

Reproducible with following OS/versions:

• Operating System: Ubunut 22.04, Windows 11
• Theia Version: Theia IDE 1.52, Current Theia master