Extract InlineCompletionProvider to its own crate (#20935)

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

crates/supermaven/Cargo.toml

@@ -16,17 +16,17 @@ doctest = false
 anyhow.workspace = true
 client.workspace = true
 collections.workspace = true
-editor.workspace = true
-gpui.workspace = true
 futures.workspace = true
+gpui.workspace = true
+inline_completion.workspace = true
 language.workspace = true
 log.workspace = true
 postage.workspace = true
 serde.workspace = true
 serde_json.workspace = true
 settings.workspace = true
-supermaven_api.workspace = true
 smol.workspace = true
+supermaven_api.workspace = true
 text.workspace = true
 ui.workspace = true
 unicode-segmentation.workspace = true

crates/supermaven/src/supermaven_completion_provider.rs

@@ -1,9 +1,9 @@
 use crate::{Supermaven, SupermavenCompletionStateId};
 use anyhow::Result;
 use client::telemetry::Telemetry;
-use editor::{CompletionProposal, Direction, InlayProposal, InlineCompletionProvider};
 use futures::StreamExt as _;
 use gpui::{AppContext, EntityId, Model, ModelContext, Task};
+use inline_completion::{CompletionProposal, Direction, InlayProposal, InlineCompletionProvider};
 use language::{language_settings::all_language_settings, Anchor, Buffer, BufferSnapshot};
 use std::{
     ops::{AddAssign, Range},