"Open in Terminal" should create tab in a predictable way when more than one Terminal window exists

## Problem
If you have more than one Terminal window and then use the "Open in Terminal" option in Files or Code, or type `io,elementary,terminal -t ` into a shell the newly created tab is made in the last opened window - which could be on a different workspace.= so it may appear nothing happened.

## Proposal
The new tab is created in the most recently focused Terminal window.

## Prior Art
An alternative would be to always open a new window on the current workspace (like e.g. Mate Terminal)