lsp: Provide completion reason in the request (#12893)

This should help LS make a better call about the completions it should
return back to the caller. For example, it speeds up import completions
for typescript.
Before: 


https://github.com/zed-industries/zed/assets/24362066/b38fd565-f9ff-4db7-a87f-c3b31a9fdc96

after: 


https://github.com/zed-industries/zed/assets/24362066/d4fbc9ae-9aab-4543-b9f6-16acf1619576


This should be merged after 06.12 Preview to give it some time on
Nightly.

Release Notes:

- N/A

crates/lsp/src/lsp.rs

@@ -1061,7 +1061,7 @@ impl LanguageServer {
             select! {
                 response = rx.fuse() => {
                     let elapsed = started.elapsed();
-                    log::trace!("Took {elapsed:?} to receive response to {method:?} id {id}");
+                    log::info!("Took {elapsed:?} to receive response to {method:?} id {id}");
                     cancel_on_drop.abort();
                     response?
                 }