Add basic vi motion support for terminal (#18715)

Closes #7417

Release Notes:

- Added basic support for Alacritty's [vi
mode](https://github.com/alacritty/alacritty/blob/master/docs/features.md#vi-mode)
to the built-in terminal (which is using Alacritty under the hood.) The
vi mode can be activated with `ctrl-shift-space` and then supports some
basic motions to navigate through the terminal's scrollback buffer.

## Details

Leverages existing selection functionality from mouse_drag and the
ViMotion API of alacritty to add basic vi motions in the terminal.
Please note, this is only basic functionality (move, select, and yank to
system clipboard) and not a fully functional vim environment (e.g.
search, configurable keybindings, and paste). I figured this would be an
interim solution to the long term, more fleshed out, solution proposed
by @mrnugget.

Ctrl+Shift+Space to enter Vi mode while in the terminal (Same default
binding in alacritty)

assets/keymaps/default-linux.json

@@ -664,7 +664,8 @@
       "shift-up": "terminal::ScrollLineUp",
       "shift-down": "terminal::ScrollLineDown",
       "shift-home": "terminal::ScrollToTop",
-      "shift-end": "terminal::ScrollToBottom"
+      "shift-end": "terminal::ScrollToBottom",
+      "ctrl-shift-space": "terminal::ToggleViMode"
     }
   },
   {