There's more than one emacs terminal (for some reason), and term is the most broken one and can't even handle a title. Fixes #7122.
fish_title
Closes #5517. Credit goes to @jadenPete. [skip-ci]
The prompt is a fallback that is overridden via a function file anyway. Do that with the title as well, so we can use just builtins. This removes error messages when $fish_function_path is borked.