If the user already binds `tab`/`alt-tab`/`alt-l` to a different action
in a conflicting context and hasn't assigned a different keybinding for
`editor::AcceptEditPrediction`, we would show broken popovers with no
bindings:

Instead, they will now see an error-variant of every popover which
includes a tooltip with a short description and buttons to open the
keymap, and open a new docs section explaining the issue in detail and
how to fix it.

Note: I included the docs change in this PR because it's ok to deploy
before the release, as it also applies to existing versions.
Release Notes:
- edit predictions: Improve UX when there's no keybinding for accepting
predictions
---------
Co-authored-by: Danilo Leal <daniloleal09@gmail.com>
Co-authored-by: Danilo <danilo@zed.dev>