Hide the menubar when menus lose focus (if toggled off)

[droidmonkey]

• Fixes Menubar is not hidden automatically when there is no focus #10768
• Also fix menubar toggling not working if Qt version is less than 5.15

Testing strategy

Tested manually

Type of change

• ✅ Bug fix (non-breaking change that fixes an issue)

[codecov]

Codecov Report

Attention: Patch coverage is 31.25000% with 11 lines in your changes missing coverage. Please review.

Project coverage is 63.72%. Comparing base (d57d167) to head (fb5dd1e).

Files with missing lines	Patch %	Lines
src/gui/MainWindow.cpp	31.25%	11 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop   #11355      +/-   ##
===========================================
+ Coverage    63.71%   63.72%   +0.01%     
===========================================
  Files          362      362              
  Lines        38000    38014      +14     
===========================================
+ Hits         24210    24222      +12     
- Misses       13790    13792       +2     

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[varjolintu]

This doesn't work properly. If you follow these steps, you cannot get the menubar back until you've changed the option via Application Settings:

1. Disable the Show Menubar option from menu. Confirm that it works properly.
2. Enable the Show Menubar option from menu.
3. Menu bar goes hidden again. You cannot get it back even when pressing Alt. Is the timer still running? Or the options is not actually checked?
4. Go to Application Settings and change the value of Show Menubar. Everything works again.

[droidmonkey]

Oops, forgot to guard the timer with the config setting

[droidmonkey]

@varjolintu fixed

[droidmonkey]

Cleaned up the code logic a little bit and reduced the timeout to 250ms. 1 second resulted in weird delays.

[xboxones1]

It works well, but I don't know how critical it is, hiding with Alt button sometimes works incorrectly. Instead of hiding the menu, the first menu item is opened.

[varjolintu]

Dunno if it's worth saving the last menu opened?

[droidmonkey]

Pressing ALT in the situation shown in the video should hide the menu bar, will have to look into that.