Visual Editor: Wait for saved pane settings before relaunch (#13323)

Wait for pane settings to reach disk before terminating and relaunching the editor in the pane tests.
The preview queues settings updates for the host, while the testing context terminates the process on exit.
A successful UI reset therefore does not guarantee that the reset has been saved.

Keep the double-click reset and the relaunch assertions.
Assert the final UI reset, then use the existing condition-based wait to observe the saved reset.
First observe the saved 120-pixel height, so older default settings cannot satisfy the reset check.
Apply the same persistence boundary to the pane-size relaunch test.