zed_extension_api: Add HttpRequestBuilder (#16165)

This PR adds an `HttpRequestBuilder` to the extension API to allow for a
more ergonomic way for constructing HTTP requests within extensions.

The HTTP client functionality is now also exposed via the
`zed_extension_api::http_client` module instead of top-level.

Release Notes:

- N/A

crates/extension_api/src/extension_api.rs

@@ -1,6 +1,6 @@
 //! The Zed Rust Extension API allows you write extensions for [Zed](https://zed.dev/) in Rust.
 
-/// Provides access to Zed settings.
+pub mod http_client;
 pub mod settings;
 
 use core::fmt;
@@ -19,10 +19,6 @@ pub use wit::{
         github_release_by_tag_name, latest_github_release, GithubRelease, GithubReleaseAsset,
         GithubReleaseOptions,
     },
-    zed::extension::http_client::{
-        fetch, fetch_stream, HttpMethod, HttpRequest, HttpResponse, HttpResponseStream,
-        RedirectPolicy,
-    },
     zed::extension::nodejs::{
         node_binary_path, npm_install_package, npm_package_installed_version,
         npm_package_latest_version,