Fix session being persisted even when disabled

[lhecker]

This fixes 2 bugs:

• PersistState being called when the window is closed
  (as opposed to closing the tab). The settings check was missing.
• Session cleanup running depending on whether the feature is
  currently enabled as opposed to whether it was enabled on launch.

Closes #17206
Closes #17207

Validation Steps Performed

• Create a bunch of leftover buffer_*.txt files by running
  the current Dev version off of main
• Build this branch, then open and close a window
• All buffer_*.txt are gone and state.json is cleaned up ✅

[DHowett]

Can you make sure this works properly in the multi-window case?

2 windows 2 tabs cases:

• Close the second window with the X
• Close the second window by closing each tab individually
• Quit the application with all 4 tabs open by using command palette Quit

[carlos-zamora]

Closes #17211

Closes this PR? haha

[lhecker]

@DHowett When you say "this works" what do you mean: That it persists or that it doesn't persist?

If it's the latter, then yes this will work, because PersistState() is only ever called if ShouldUsePersistedLayout() is true. There's no alternate way to get into the PersistState() call that gets past this condition. Of course I can test this later, but this PR is IMO good to go.

[DHowett]

If it's the latter, then yes this will work, because PersistState() is only ever called if ShouldUsePersistedLayout() is true.

ShouldUsePersistedLayout only reflects the user's preferences, it does not make any decisions based on how many windows currently exist.

I expect the top two cases to NOT persist, and the bottom case to persist two windows.

[lhecker]

Oh I get what you mean now. So, the difference is AppHost::_CloseRequested() vs. AppHost::_quit() and its callback AppHost::_QuitRequested.

_CloseRequested() is called when the last tab of a window is closed or you close a window and there's more than one left. _quit() is called when using "Quit all". It's also called when there's only 1 window is left (see _CloseRequested() and its GetNumberOfPeasants()).

I'll test it but I think this should be helpful for understanding how it works. 😅

[lhecker]

Alright, I hope I tested it properly, but it seemed to work correctly.