chore: Extract PromptStore out of prompt_library (#25837)

One step closer to removing long pole with assistant/assistant2 builds

Release Notes:

- N/A

crates/zed/src/main.rs

@@ -23,7 +23,7 @@ use gpui::{App, AppContext as _, Application, AsyncApp, UpdateGlobal as _};
 use gpui_tokio::Tokio;
 use http_client::{read_proxy_from_env, Uri};
 use language::LanguageRegistry;
-use prompt_library::PromptBuilder;
+use prompt_store::PromptBuilder;
 use reqwest_client::ReqwestClient;
 
 use assets::Assets;