Fabric: New names for ContextContainer methods

Summary:
... and slighly new behaviour for one of them.

The method does nothing if given `key` already exists in the container.

This diff finishes the transition of ContextContainer from an internal bag of things with unclear yet ownership into a legit dedicated dependency injection container for the product code.

The original names of methods imply that the container can have only one object of a given type which is no longer true. The new API is much more generic and idiomatic to C++, it mimics `std:map` API which is intuitive to anyone who familiar with C++ containers.

Besides the naming, `insert` method changed the semantic a bit; now it does nothing in case of inserting an object with a key that already exists. That might seem counterintuitive for "normal" people, but C++ has some wired reasons for that and, hopefully, it's expected behavior in the C++ community.

Fun fact: We need this to fix hot-reload.

Reviewed By: sahrens

Differential Revision: D15681736

fbshipit-source-id: 194f342528446a911eaf072ba3a94a5d8af3cb52

ReactAndroid/src/main/java/com/facebook/react/fabric/jni/Binding.cpp

@@ -136,8 +136,8 @@ void Binding::installFabricUIManager(
 
   std::shared_ptr<const ReactNativeConfig> config =
       std::make_shared<const ReactNativeConfigHolder>(reactNativeConfig);
-  contextContainer->registerInstance(config, "ReactNativeConfig");
-  contextContainer->registerInstance(javaUIManager_, "FabricUIManager");
+  contextContainer->insert("ReactNativeConfig", config);
+  contextContainer->insert("FabricUIManager", javaUIManager_);
 
   auto toolbox = SchedulerToolbox{};
   toolbox.contextContainer = contextContainer;