Replace isahc with async ureq (#18414)

REplace isahc with ureq everywhere gpui is used.

This should allow us to make http requests without libssl; and avoid a
long-tail of panics caused by ishac.

Release Notes:

- (potentially breaking change) updated our http client

---------

Co-authored-by: Mikayla <mikayla@zed.dev>

crates/extension_cli/src/main.rs

@@ -13,8 +13,8 @@ use extension::{
     extension_builder::{CompileExtensionOptions, ExtensionBuilder},
     ExtensionManifest,
 };
-use isahc_http_client::IsahcHttpClient;
 use language::LanguageConfig;
+use reqwest_client::ReqwestClient;
 use theme::ThemeRegistry;
 use tree_sitter::{Language, Query, WasmStore};
 
@@ -66,12 +66,7 @@ async fn main() -> Result<()> {
         std::env::consts::OS,
         std::env::consts::ARCH
     );
-    let http_client = Arc::new(
-        IsahcHttpClient::builder()
-            .default_header("User-Agent", user_agent)
-            .build()
-            .map(IsahcHttpClient::from)?,
-    );
+    let http_client = Arc::new(ReqwestClient::user_agent(&user_agent)?);
 
     let builder = ExtensionBuilder::new(http_client, scratch_dir);
     builder