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/command_palette_hooks/Cargo.toml

@@ -0,0 +1,14 @@
+[package]
+name = "command_palette_hooks"
+version = "0.1.0"
+edition = "2021"
+publish = false
+license = "GPL-3.0-or-later"
+
+[lib]
+path = "src/command_palette_hooks.rs"
+doctest = false
+
+[dependencies]
+collections.workspace = true
+gpui.workspace = true

crates/command_palette_hooks/LICENSE-GPL

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

crates/command_palette_hooks/src/command_palette_hooks.rs

@@ -0,0 +1,24 @@
+use std::any::TypeId;
+
+use collections::HashSet;
+use gpui::{Action, AppContext, Global};
+
+#[derive(Default)]
+pub struct CommandPaletteFilter {
+    pub hidden_namespaces: HashSet<&'static str>,
+    pub hidden_action_types: HashSet<TypeId>,
+}
+
+impl Global for CommandPaletteFilter {}
+
+pub struct CommandPaletteInterceptor(
+    pub Box<dyn Fn(&str, &AppContext) -> Option<CommandInterceptResult>>,
+);
+
+impl Global for CommandPaletteInterceptor {}
+
+pub struct CommandInterceptResult {
+    pub action: Box<dyn Action>,
+    pub string: String,
+    pub positions: Vec<usize>,
+}