Export moduleIsInitialized from RCTModuleRegistry

Summary:
## Context
Product code can query the Bridge, or the TurboModuleManager, to see whether a native module has been initialized or not. But, this API doesn't exist in RCTModuleRegistry.

## Changes
This diff exports moduleIsInitialized: from RCTModuleRegistry. That way, RCTBridgeProxy (introduce in D46088752) can more easily implement the moduleIsInitialized: API.

Changelog:
[iOS][Added] - Introduce RCTModuleRegistry moduleIsInitialized:

Reviewed By: cortinico

Differential Revision: D46166548

fbshipit-source-id: c9954273e511083276aeb911dd58719cf4a11f10

packages/react-native/React/Base/RCTBridgeModule.h

@@ -390,6 +390,7 @@ RCT_EXTERN_C_END
 
 - (id)moduleForName:(const char *)moduleName;
 - (id)moduleForName:(const char *)moduleName lazilyLoadIfNecessary:(BOOL)lazilyLoad;
+- (BOOL)moduleIsInitialized:(Class)moduleClass;
 @end
 
 typedef UIView * (^RCTBridgelessComponentViewProvider)(NSNumber *);

packages/react-native/React/Base/RCTModuleRegistry.m

@@ -47,4 +47,21 @@ - (id)moduleForName:(const char *)moduleName lazilyLoadIfNecessary:(BOOL)lazilyL
   return module;
 }
 
+- (BOOL)moduleIsInitialized:(Class)moduleClass
+{
+  RCTBridge *bridge = _bridge;
+
+  if (bridge) {
+    return [bridge moduleIsInitialized:moduleClass];
+  }
+
+  id<RCTTurboModuleRegistry> turboModuleRegistry = _turboModuleRegistry;
+  if (turboModuleRegistry) {
+    NSString *moduleName = RCTBridgeModuleNameForClass(moduleClass);
+    return [turboModuleRegistry moduleIsInitialized:[moduleName UTF8String]];
+  }
+
+  return NO;
+}
+
 @end