This changes #22093 by making the change only have an effect for the
supported provider: Zeta.
Made the change because the UX is still experimental and I don't want to
break existing workflows for Copilot/Supermaven users.
Even Zeta users can opt-out of it by setting
`"show_inline_completions_in_menu": false` in their settings, in case
they want the old show-inline-completion-or-show-lsp-completion behavior
back.
Release Notes:
- N/A
This PR extracts the `InlineCompletionProvider` trait and its related
types out of `editor` and into a new `inline_completion` crate.
By doing so we're able to remove a dependency on `editor` from the
`copilot` and `supermaven` crates.
We did have to move `editor::Direction` into the `inline_completion`
crate, as it is referenced by the `InlineCompletionProvider`. This
should find a better home, at some point.
Release Notes:
- N/A
