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>

Cargo.lock

@@ -9208,6 +9208,7 @@ version = "0.1.0"
 dependencies = [
  "anyhow",
  "async-compression",
+ "async-fs",
  "async-tar",
  "async-trait",
  "chrono",
@@ -9239,9 +9240,11 @@ dependencies = [
  "serde_json",
  "serde_json_lenient",
  "settings",
+ "sha2",
  "smol",
  "snippet_provider",
  "task",
+ "tempfile",
  "text",
  "theme",
  "toml 0.8.20",