assistant: Remove low_speed_timeout (#20681)

This removes the `low_speed_timeout` setting from all providers as a
response to issue #19509.

Reason being that the original `low_speed_timeout` was only as part of
#9913 because users wanted to _get rid of timeouts_. They wanted to bump
the default timeout from 5sec to a lot more.

Then, in the meantime, the meaning of `low_speed_timeout` changed in
#19055 and was changed to a normal `timeout`, which is a different thing
and breaks slower LLMs that don't reply with a complete response in the
configured timeout.

So we figured: let's remove the whole thing and replace it with a
default _connect_ timeout to make sure that we can connect to a server
in 10s, but then give the server as long as it wants to complete its
response.

Closes #19509

Release Notes:

- Removed the `low_speed_timeout` setting from LLM provider settings,
since it was only used to _increase_ the timeout to give LLMs more time,
but since we don't have any other use for it, we simply remove the
setting to give LLMs as long as they need.

---------

Co-authored-by: Antonio <antonio@zed.dev>
Co-authored-by: Peter Tripp <peter@zed.dev>

crates/http_client/src/http_client.rs

@@ -13,21 +13,10 @@ use std::fmt;
 use std::{
     any::type_name,
     sync::{Arc, Mutex},
-    time::Duration,
 };
 pub use url::Url;
 
-#[derive(Clone, Debug)]
-pub struct ReadTimeout(pub Duration);
-
-impl Default for ReadTimeout {
-    fn default() -> Self {
-        Self(Duration::from_secs(5))
-    }
-}
-
 #[derive(Default, Debug, Clone, PartialEq, Eq, Hash)]
-
 pub enum RedirectPolicy {
     #[default]
     NoFollow,
@@ -37,20 +26,11 @@ pub enum RedirectPolicy {
 pub struct FollowRedirects(pub bool);
 
 pub trait HttpRequestExt {
-    /// Set a read timeout on the request.
-    /// For isahc, this is the low_speed_timeout.
-    /// For other clients, this is the timeout used for read calls when reading the response.
-    /// In all cases this prevents servers stalling completely, but allows them to send data slowly.
-    fn read_timeout(self, timeout: Duration) -> Self;
     /// Whether or not to follow redirects
     fn follow_redirects(self, follow: RedirectPolicy) -> Self;
 }
 
 impl HttpRequestExt for http::request::Builder {
-    fn read_timeout(self, timeout: Duration) -> Self {
-        self.extension(ReadTimeout(timeout))
-    }
-
     fn follow_redirects(self, follow: RedirectPolicy) -> Self {
         self.extension(follow)
     }