Sorting and ordering has now been split apart. The ImportanceAlgorithm also finally makes use of the sorting.
So far metrics look okay at 3ms for a simple account, though this could potentially get worse due to the multiple loops involved (one for tags, one for categories, one for ordering). We might be able to feed a whole list of rooms into the thing and have it regenerate the lists on demand.
This is to get around the problem of a slow dispatch loop. Instead of slowing the whole app down to deal with room lists, we'll just raise events to say we're ready.
Based upon the EventEmitter class.
This does a number of things (sorry):
* Estimates the type changes needed to the dispatcher (later to be replaced by https://github.com/matrix-org/matrix-react-sdk/pull/4593)
* Sets up the stack for a whole new room list store, and later components for usage.
* Create a proxy class to ensure the app still functions as expected when the various stores are enabled/disabled
* Demonstrates a possible structure for algorithms
