Folds the top-level `shutdown()` function into a method of `ShutdownHandle` and then simply stores `ShutdownHandle` on `LoginServer` since the two fields it contains were always being used together, anyway. --- [//]: # (BEGIN SAPLING FOOTER) Stack created with [Sapling](https://sapling-scm.com). Best reviewed with [ReviewStack](https://reviewstack.dev/openai/codex/pull/2396). * #2399 * #2398 * __->__ #2396 * #2395 * #2394 * #2393 * #2389