[v6] Implement ML-Kit Natural Language (#2117)

 - Implement ML-Kit Natural Language (#2117)
 - Includes additional refactor changes across other modules for internals api reworking

Author: Salakar

CHANGELOG.md

@@ -184,16 +184,20 @@ await analytics().setUserId('12345678');
 
 ## Remote Config (config)
 
-- [NEW] Added a new `fetchAndActivate` method - this fetches the config and activate it without the need to call `activateFetch()` separately
-- [NEW] Added a new `getConfigSettings` method - this provides the following properties; `lastFetchTime`, `lastFetchStatus` & `isDeveloperModeEnabled`
+- [NEW] Added a new `fetchAndActivate` method - this fetches the config and activate it without the need to call `activate()` separately
+- [NEW] Added the following properties to `firebase.config()`; `lastFetchTime`, `lastFetchStatus` & `isDeveloperModeEnabled`
 - [NEW] Added a new `setConfigSettings` method - this allows setting `isDeveloperModeEnabled`, replaces the `enableDeveloperMode` method
-- [NEW] Added a new `getValuesByKeysPrefix` method - this will retrieve all values where the key matches the prefix provided, this saves having to call `getKeysByPrefix` and then `getValues` separately
+- [NEW] All previous `get* ` methods have been removed and replaced with 2 synchronous methods:
+  - `getValue(key: string): ConfigValue` - returns a single configuration value `{ value, source }`
+  - `getAll(): ConfigValues` - returns all configuration values e.g. `{ some_key: { value, source }, other_key: { value, source } }`
 - [BREAKING] `setDefaultsFromResource` now returns a Promise that resolves when completed, this will reject with code `config/resouce_not_found` if the file could not be found
 - [BREAKING] `setDefaultsFromResource` now expects a resource file name for Android to match iOS, formerly this required a resource id (something you would not have in RN as this was generated at build time by Android)
   - We're writing up a guide for this on the new documentation website, showing how to use the plist/xml defaults files on each platform
 - [BREAKING] `enableDeveloperMode` has been removed, you can now use `setConfigSettings({ isDeveloperModeEnabled: boolean })` instead
 - [BREAKING] `setDefaults` now returns a Promise that resolves when completed
 
+Multi-apps is not yet supported as the Firebase iOS SDK is missing support for it.
+
 ## Storage
 
 <!-- TODO(salakar) change link -->