Detect new releases of codex-acp (#39388)

Now we use GitHub Releases to detect when there's a new version of
codex-acp out, and we notify the user in the same way we do for the
other external agents.

This also moves `github_download.rs` out of the `languages` crate and
into `http_client`, because now we're not just using it for language
servers anymore, we're also using it for external agents.

Release Notes:

- N/A

---------

Co-authored-by: Lukas Wirth <me@lukaswirth.dev>

crates/languages/src/python.rs

@@ -26,6 +26,7 @@ use std::env::consts;
 use util::fs::{make_file_executable, remove_matching};
 use util::rel_path::RelPath;
 
+use http_client::github_download::{GithubBinaryMetadata, download_server_binary};
 use parking_lot::Mutex;
 use std::str::FromStr;
 use std::{
@@ -37,8 +38,6 @@ use std::{
 use task::{ShellKind, TaskTemplate, TaskTemplates, VariableName};
 use util::{ResultExt, maybe};
 
-use crate::github_download::{GithubBinaryMetadata, download_server_binary};
-
 pub(crate) struct PyprojectTomlManifestProvider;
 
 impl ManifestProvider for PyprojectTomlManifestProvider {
@@ -272,7 +271,7 @@ impl LspInstaller for TyLspAdapter {
         }
 
         download_server_binary(
-            delegate,
+            &*delegate.http_client(),
             &url,
             expected_digest.as_deref(),
             &destination_path,
@@ -2116,7 +2115,7 @@ impl LspInstaller for RuffLspAdapter {
         }
 
         download_server_binary(
-            delegate,
+            &*delegate.http_client(),
             &url,
             expected_digest.as_deref(),
             &destination_path,