Restoring exited panes should not restart them

[lhecker]

Description of the new feature/enhancement

• Have session persistence enabled
• Have a pane that has exited but wasn't closed, because the termination behavior is "never", etc.
• Restart Windows Terminal
• Suddenly all those tabs are running again

We should avoid restarting such tabs.

Proposed technical implementation details (optional)

The state.json should store whether a pane has exited. If it had then it should not restart it automatically.

[DHowett]

I just had the same thought a couple days ago! We totally should.