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/Cargo.toml

@@ -13,11 +13,11 @@ doctest = false
 anyhow.workspace = true
 client.workspace = true
 collections.workspace = true
-# HACK: We're only depending on `copilot` here for `CommandPaletteFilter`.  See the attached comment on that type.
-copilot.workspace = true
+command_palette_hooks.workspace = true
 fuzzy.workspace = true
 gpui.workspace = true
 picker.workspace = true
+postage.workspace = true
 project.workspace = true
 release_channel.workspace = true
 serde.workspace = true
@@ -27,7 +27,6 @@ ui.workspace = true
 util.workspace = true
 workspace.workspace = true
 zed_actions.workspace = true
-postage.workspace = true
 
 [dev-dependencies]
 ctor.workspace = true