Extract VimModeSetting to its own crate (#21019)

This PR extracts the `VimModeSetting` out of the `vim` crate and into
its own `vim_mode_setting` crate.

A number of crates were depending on the entirety of the `vim` crate
just to reference `VimModeSetting`, which was not ideal.

Release Notes:

- N/A

crates/vim_mode_setting/Cargo.toml

@@ -0,0 +1,17 @@
+[package]
+name = "vim_mode_setting"
+version = "0.1.0"
+edition = "2021"
+publish = false
+license = "GPL-3.0-or-later"
+
+[lints]
+workspace = true
+
+[lib]
+path = "src/vim_mode_setting.rs"
+
+[dependencies]
+anyhow.workspace = true
+gpui.workspace = true
+settings.workspace = true

crates/vim_mode_setting/LICENSE-GPL

@@ -0,0 +1 @@
+../../LICENSE-GPL

crates/vim_mode_setting/src/vim_mode_setting.rs

@@ -0,0 +1,36 @@
+//! Contains the [`VimModeSetting`] used to enable/disable Vim mode.
+//!
+//! This is in its own crate as we want other crates to be able to enable or
+//! disable Vim mode without having to depend on the `vim` crate in its
+//! entirety.
+
+use anyhow::Result;
+use gpui::AppContext;
+use settings::{Settings, SettingsSources};
+
+/// Initializes the `vim_mode_setting` crate.
+pub fn init(cx: &mut AppContext) {
+    VimModeSetting::register(cx);
+}
+
+/// Whether or not to enable Vim mode.
+///
+/// Default: false
+pub struct VimModeSetting(pub bool);
+
+impl Settings for VimModeSetting {
+    const KEY: Option<&'static str> = Some("vim_mode");
+
+    type FileContent = Option<bool>;
+
+    fn load(sources: SettingsSources<Self::FileContent>, _: &mut AppContext) -> Result<Self> {
+        Ok(Self(
+            sources
+                .user
+                .or(sources.server)
+                .copied()
+                .flatten()
+                .unwrap_or(sources.default.ok_or_else(Self::missing_default)?),
+        ))
+    }
+}