chore: Prepare for Rust edition bump to 2024 (without autofix) (#27791)

Successor to #27779 - in this PR I've applied changes manually, without
futzing with if let lifetimes at all.

Release Notes:

- N/A

crates/prompt_store/src/prompt_store.rs

@@ -117,7 +117,7 @@ impl MetadataCache {
 }
 
 impl PromptStore {
-    pub fn global(cx: &App) -> impl Future<Output = Result<Arc<Self>>> {
+    pub fn global(cx: &App) -> impl Future<Output = Result<Arc<Self>>> + use<> {
         let store = GlobalPromptStore::global(cx).0.clone();
         async move { store.await.map_err(|err| anyhow!(err)) }
     }