Remember window order when focus is lost and regained

[kevin-june]

Version: 1.0.207
Platform: macOS x64 23.5.0
Plugins: none
Frontend: xterm-webgl

When multiple Tabby windows are opened, changing the focus from Tabby and back to it with the mouse results in Tabby changing the currently focused window. Tabby should respect the user's focus selection.

Steps to reproduce:

• open a first Tabby window
• open a second Tabby window
• focus on the second Tabby window
• focus on any other application
• focus on Tabby again with the mouse (not the keyboard)

Expected behavior:

• the second Tabby window should be focused
• Tabby visibly changes the focus from the second window to the first