Testing out disabling Reagent ratom/rendering queue

[Deraen]

#504 etc.

Currently test suite is getting stuck due to test using u/with-mounted-component-async and u/run-fns-after-render not finishing at all.

TODO:

• Figure out how to call after-render callbacks after React finishes the render
• New render and act utils to run checks after component is rendered
• Check and consider if we can just completely drop create-class and the class-based component implementation
  • Probably not a required change, but would make reagent code cleaner
• drop reagent.core/after-render and possibly other queue functions
  • There is no simple way to hook into React rendering queue to keep this working as previously.
    Likely this isn't used that often, so users would just replace these places with hooks manually?

[Deraen]

As I was thinking, while components aren't rendered for each Ratom change due to the React queue, here the reaction body is running each time input Ratoms change, which is potentially a (big) problem for re-frame.

Consider cases where text input value is used as a reaction (or subscription) input.