Speed up @cachedList (#13591)

This speeds things up by ~2x.

The vast majority of the time is now spent in `LruCache` moving things around the linked lists.

We do this via two things:
1. Don't create a deferred per-key during bulk set operations in `DeferredCache`. Instead, only create them if a subsequent caller asks for the key.
2. Add a bulk lookup API to `DeferredCache` rather than use a loop.

changelog.d/13591.misc

@@ -0,0 +1 @@
+Improve performance of `@cachedList`.