chore: remove unused lib/discovery crate [Cherry-pick to 0.8] (#5279)

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

Author: nnshah1

Cargo.lock

@@ -14,7 +14,6 @@ members = [
     "lib/bindings/c",
     "lib/bindings/python/codegen",
     "lib/engines/*",
-    "lib/discovery",
     "lib/config",
 ]
 # Exclude certain packages that are slow to build and we don't ship as flagship