[MacOS] Option key is inconsistently mapped between Terminal and GUI shell

**Describe the bug**
The Option key on MacOS is inconsistently mapped between the system Terminal app and the Multipass shell in the GUI. The terminal will allow the insertion of special characters with Option, but the GUI will simply ignore the use of the Option key.

*Originally posted by @paul-peeler in https://discourse.ubuntu.com/t/meta-key-in-multipass-app/56017/2*

Start by reproducing the Option-key behavior in the MacOS system Terminal and the Multipass GUI shell, then trace how the GUI handles keyboard input. Done means Option produces the expected special characters in the GUI shell instead of being ignored, with the behavior consistent with Terminal.

Written by the indexing model from the issue text.