also clean up unused canary values

This will allow third party apps to use these in their code

* export Context instead of just Consumer/Provider
* fix error messages for removed functionality
* minor displayName change

when the time is right, one need only
change the BABEL_ENV for build:umd:min back to "rollup-production"

* React.forwardRef is VERY slow, on the order of 2x slower in our benchmark. So we only enable it if withRef="forwardRef" folks using withRef=true will get an error telling them to update and not rely on getWrappedInstance() but just to use the ref directly
* renderCountProp is removed, as this is natively supported in React dev tools now
* all usages of shallowEquals are removed for pure components, it was unnecessary.
* instead of allowing passing in a custom Context consumer in props, it is now required to be passed in via connect options at declaration time.

Ported connect test handling from 995
Deduped the "custom store context" messages
Removed use of observedBits for now
Commented out derivedProps propTypes that caused test failures

Removed use of PureWrapper
Used React.memo() on the wrapped component
Renamed and extracted makeDerivedPropsSelector
Added makeChildElementSelector
Simplified render props callback
Simplified forwardRef handling