Verify downloaded rust-analyzer and clang binaries by checking the artifact digest (#35642)

Release Notes:

- Added GitHub artifact digest verification for rust-analyzer and clangd
binary downloads, skipping downloads if cached binary digest is up to
date
- Added verification that cached rust-analyzer and clangd binaries are
executable, if not they are redownloaded

---------

Co-authored-by: Kirill Bulatov <kirill@zed.dev>

crates/http_client/src/github.rs

@@ -8,6 +8,7 @@ use url::Url;
 pub struct GitHubLspBinaryVersion {
     pub name: String,
     pub url: String,
+    pub digest: Option<String>,
 }
 
 #[derive(Deserialize, Debug)]
@@ -24,6 +25,7 @@ pub struct GithubRelease {
 pub struct GithubReleaseAsset {
     pub name: String,
     pub browser_download_url: String,
+    pub digest: Option<String>,
 }
 
 pub async fn latest_github_release(