dillon1000/react

[be][env] Move EnvironmentOptions -> EnvironmentConfig

--- 

Simplify Environment options by: 

- EnvironmentOptions -> EnvironmentConfig 

config is now directly passed around instead of being eagerly merged. 

- Moving merging / initialization logic into `Environment` constructor. From my 
understanding, there is no need to decouple merged options from an environment. 

This prepares Environment for the next PR, which adds non-stateful properties to 
Environment (i.e. a `GlobalRegistry`) that should be converted from config 
values (i.e. not directly exposed to the user due to potentially inconsistent 
inputs)