Fix: requeue events, process events

[jkelleyrtp]

• Fix use_resource cancels spawn_forever's future (and even regular spawn) when listening to signals set by said future #2235 by requeuing tasks
• Fix Reading a resource breaks reactivity #2225 by requeuing tasks

Also fixes the memochain example by calling process_events in more places.

This code needs to be refactored/lightly rewritten since we've done a lot of work with suspense and memos recently. These are little bugs that should be easy to catch.