GTK: Implement tab title renaming

[mitchellh]

Follow on from macOS here: #9879

This should be fairly simple: reacting to the prompt_title apprt action and setting up all the bindings.

[dmatos2012]

I'd like to work on this. Im checking out your macOS impl and looks friendly for people new to the codebase. I know we dont assign here, but giving it a shot anyways!