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/languages/src/lib.rs

@@ -17,6 +17,7 @@ use crate::{json::JsonTaskProvider, python::BasedPyrightLspAdapter};
 mod bash;
 mod c;
 mod css;
+mod github_download;
 mod go;
 mod json;
 mod package_json;