Add an eval binary that evaluates our semantic index against CodeSearchNet (#17375)

This PR is the beginning of an evaluation framework for our AI features.
Right now, we're evaluating our semantic search feature against the
[CodeSearchNet](https://github.com/github/CodeSearchNet) code search
dataset. This dataset is very limited (for the most part, only 1 known
good search result per repo) but it has surfaced some problems with our
search already.

Release Notes:

- N/A

---------

Co-authored-by: Jason <jason@zed.dev>
Co-authored-by: Jason Mancuso <7891333+jvmncs@users.noreply.github.com>
Co-authored-by: Nathan <nathan@zed.dev>
Co-authored-by: Richard <richard@zed.dev>

crates/http_client/src/http_client.rs

@@ -5,6 +5,7 @@ use derive_more::Deref;
 use futures::future::BoxFuture;
 use futures_lite::FutureExt;
 use isahc::config::{Configurable, RedirectPolicy};
+pub use isahc::http;
 pub use isahc::{
     http::{Method, StatusCode, Uri},
     AsyncBody, Error, HttpClient as IsahcHttpClient, Request, Response,
@@ -226,7 +227,7 @@ pub fn client(user_agent: Option<String>, proxy: Option<Uri>) -> Arc<dyn HttpCli
         // those requests use a different http client, because global timeouts
         // of 50 and 60 seconds, respectively, would be very high!
         .connect_timeout(Duration::from_secs(5))
-        .low_speed_timeout(100, Duration::from_secs(5))
+        .low_speed_timeout(100, Duration::from_secs(30))
         .proxy(proxy.clone());
     if let Some(user_agent) = user_agent {
         builder = builder.default_header("User-Agent", user_agent);