chore: Bump Rust version to 1.88 (#33439)

Goodies in this version:
- if-let chains 🎉
- Better compiler perf for Zed
(https://github.com/rust-lang/rust/pull/138522)

For more, see: https://releases.rs/docs/1.88.0/

Release Notes:

- N/A

---------

Co-authored-by: Junkui Zhang <364772080@qq.com>

crates/collab/src/db/tests/embedding_tests.rs

@@ -76,7 +76,10 @@ async fn test_purge_old_embeddings(cx: &mut gpui::TestAppContext) {
     db.purge_old_embeddings().await.unwrap();
 
     // Try to retrieve the purged embeddings
-    let retrieved_embeddings = db.get_embeddings(model, &[digest.clone()]).await.unwrap();
+    let retrieved_embeddings = db
+        .get_embeddings(model, std::slice::from_ref(&digest))
+        .await
+        .unwrap();
     assert!(
         retrieved_embeddings.is_empty(),
         "Old embeddings should have been purged"

crates/collab/src/rpc.rs

@@ -179,7 +179,7 @@ struct Session {
 }
 
 impl Session {
-    async fn db(&self) -> tokio::sync::MutexGuard<DbHandle> {
+    async fn db(&self) -> tokio::sync::MutexGuard<'_, DbHandle> {
         #[cfg(test)]
         tokio::task::yield_now().await;
         let guard = self.db.lock().await;
@@ -1037,7 +1037,7 @@ impl Server {
         }
     }
 
-    pub async fn snapshot(self: &Arc<Self>) -> ServerSnapshot {
+    pub async fn snapshot(self: &Arc<Self>) -> ServerSnapshot<'_> {
         ServerSnapshot {
             connection_pool: ConnectionPoolGuard {
                 guard: self.connection_pool.lock(),