Add command_palette_hooks crate (#8398)

This PR introduces a new `command_palette_hooks` crate that contains the
types used to hook into the behavior of the command palette.

The `CommandPaletteFilter` was previously extracted to the `copilot`
crate in #7095, solely because that was the earliest ancestor of the
crates that depended on it.

The `CommandPaletteInterceptor` was still defined in `command_palette`
itself.

Both of these types were consumed by other crates wanting to influence
the behavior of the command palette, but required taking a dependency on
the entire `command_palette` crate in order to gain access to these
hooks.

By moving them out into their own crate, we can improve the compile
order and make crates like `vim` able to begin building sooner without
having to wait for `command_palette` to finish compiling.

Here's a comparison of the compilation graph before and after (ignore
the timings):

#### Before

<img width="332" alt="Screenshot 2024-02-25 at 12 42 29 PM"
src="https://github.com/zed-industries/zed/assets/1486634/a57c662e-fbc2-41ab-9e30-cca17afa6c73">

#### After

<img width="362" alt="Screenshot 2024-02-25 at 12 51 15 PM"
src="https://github.com/zed-industries/zed/assets/1486634/c1a6d29c-b607-4604-8f1b-e5d318bf8849">

Release Notes:

- N/A

crates/copilot/Cargo.toml

@@ -24,6 +24,7 @@ anyhow.workspace = true
 async-compression.workspace = true
 async-tar.workspace = true
 collections.workspace = true
+command_palette_hooks.workspace = true
 futures.workspace = true
 gpui.workspace = true
 language.workspace = true

crates/copilot/src/copilot.rs

@@ -3,6 +3,7 @@ use anyhow::{anyhow, Context as _, Result};
 use async_compression::futures::bufread::GzipDecoder;
 use async_tar::Archive;
 use collections::{HashMap, HashSet};
+use command_palette_hooks::CommandPaletteFilter;
 use futures::{channel::oneshot, future::Shared, Future, FutureExt, TryFutureExt};
 use gpui::{
     actions, AppContext, AsyncAppContext, Context, Entity, EntityId, EventEmitter, Global, Model,
@@ -32,17 +33,6 @@ use util::{
     ResultExt,
 };
 
-// HACK: This type is only defined in `copilot` since it is the earliest ancestor
-// of the crates that use it.
-//
-// This is not great. Let's find a better place for it to live.
-#[derive(Default)]
-pub struct CommandPaletteFilter {
-    pub hidden_namespaces: HashSet<&'static str>,
-    pub hidden_action_types: HashSet<TypeId>,
-}
-
-impl Global for CommandPaletteFilter {}
 actions!(
     copilot,
     [