macos: implement resize overlay

[mitchellh]

Implements the resize overlay configurations completely, based on #2071.

CleanShot.2024-08-10.at.20.18.50.mp4

[clason]

I think there's a small bug: resize-overlay = after-first doesn't work for me, it always shows the overlay when opening a new tab. (Neither the default nor explicitly setting the option works; resize-overlay = never works as expected, though.)

(And wouldn't it be better to check for after-first and lastSize before creating the overlay?)