Stop leaking isahc assumption (#18408)

Users of our http_client crate knew they were interacting with isahc as
they set its extensions on the request. This change adds our own
equivalents for their APIs in preparation for changing the default http
client.

Release Notes:

- N/A

crates/anthropic/Cargo.toml

@@ -20,7 +20,6 @@ anyhow.workspace = true
 chrono.workspace = true
 futures.workspace = true
 http_client.workspace = true
-isahc.workspace = true
 schemars = { workspace = true, optional = true }
 serde.workspace = true
 serde_json.workspace = true

crates/anthropic/src/anthropic.rs

@@ -6,9 +6,8 @@ use std::{pin::Pin, str::FromStr};
 use anyhow::{anyhow, Context, Result};
 use chrono::{DateTime, Utc};
 use futures::{io::BufReader, stream::BoxStream, AsyncBufReadExt, AsyncReadExt, Stream, StreamExt};
-use http_client::{AsyncBody, HttpClient, Method, Request as HttpRequest};
-use isahc::config::Configurable;
-use isahc::http::{HeaderMap, HeaderValue};
+use http_client::http::{HeaderMap, HeaderValue};
+use http_client::{AsyncBody, HttpClient, HttpRequestExt, Method, Request as HttpRequest};
 use serde::{Deserialize, Serialize};
 use strum::{EnumIter, EnumString};
 use thiserror::Error;
@@ -289,7 +288,7 @@ pub async fn stream_completion_with_rate_limit_info(
         .header("X-Api-Key", api_key)
         .header("Content-Type", "application/json");
     if let Some(low_speed_timeout) = low_speed_timeout {
-        request_builder = request_builder.low_speed_timeout(100, low_speed_timeout);
+        request_builder = request_builder.read_timeout(low_speed_timeout);
     }
     let serialized_request =
         serde_json::to_string(&request).context("failed to serialize request")?;