Introduce staff-only inline completion provider (#21739)

Release Notes:

- N/A

---------

Co-authored-by: Thorsten Ball <mrnugget@gmail.com>
Co-authored-by: Bennet <bennet@zed.dev>
Co-authored-by: Thorsten <thorsten@zed.dev>

crates/zed/Cargo.toml

@@ -126,6 +126,7 @@ vim_mode_setting.workspace = true
 welcome.workspace = true
 workspace.workspace = true
 zed_actions.workspace = true
+zeta.workspace = true
 
 [target.'cfg(target_os = "windows")'.dependencies]
 windows.workspace = true