This fixes #7401 and probably a few other things that seemed odd with
the terminal.

Turns out that `TerminalView` has `focus_in` and `focus_out` callbacks,
but they were never called. The `focus_handle` on which they were set
was not passed in to `TerminalView`.

That meant that the `impl FocusableView for TerminalView` never returned
the focus handle with the right callbacks.

This change here uses the already created focus handle and passes it in,
so that `focus_in` and `focus_out` are now correctly called.

Release Notes:

- Fixed terminal not handling focus-state correctly and, for example,
not restoring cursor blinking state correctly.
([#7401](https://github.com/zed-industries/zed/issues/7401)).