Add additional terminal emulators to gio
This includes, in order of priority:
This allows systems without a default GNOME-approved terminal installed to launch desktop applications that use Terminal=true.
Test Plan: Launch htop in all the added terminals, and phoronix-test-suite in a couple of them
Reviewers: Triage Team, DataDrake
Reviewed By: Triage Team, DataDrake
Differential Revision: https://dev.getsol.us/D8835