Restore HTTP client transition, but use reqwest everywhere (#19055)

Release Notes:

- N/A

crates/collab/src/llm.rs

@@ -23,7 +23,7 @@ use collections::HashMap;
 use db::TokenUsage;
 use db::{usage_measure::UsageMeasure, ActiveUserCount, LlmDatabase};
 use futures::{Stream, StreamExt as _};
-use isahc_http_client::IsahcHttpClient;
+use reqwest_client::ReqwestClient;
 use rpc::{
     proto::Plan, LanguageModelProvider, PerformCompletionParams, EXPIRED_LLM_TOKEN_HEADER_NAME,
 };
@@ -44,7 +44,7 @@ pub struct LlmState {
     pub config: Config,
     pub executor: Executor,
     pub db: Arc<LlmDatabase>,
-    pub http_client: IsahcHttpClient,
+    pub http_client: ReqwestClient,
     pub clickhouse_client: Option<clickhouse::Client>,
     active_user_count_by_model:
         RwLock<HashMap<(LanguageModelProvider, String), (DateTime<Utc>, ActiveUserCount)>>,
@@ -70,11 +70,8 @@ impl LlmState {
         let db = Arc::new(db);
 
         let user_agent = format!("Zed Server/{}", env!("CARGO_PKG_VERSION"));
-        let http_client = IsahcHttpClient::builder()
-            .default_header("User-Agent", user_agent)
-            .build()
-            .map(IsahcHttpClient::from)
-            .context("failed to construct http client")?;
+        let http_client =
+            ReqwestClient::user_agent(&user_agent).context("failed to construct http client")?;
 
         let this = Self {
             executor,