RCTNetworking: Use RCTModuleRegistry to load handlers

Summary:
## Context
A React Native application can configure its RCTNetworking by initializing it with id<RCTURLRequestHandler> objects.

Therefore, RCTNetworking supports this initializer:
```
- (instancetype)initWithHandlersProvider:(NSArray<id<RCTURLRequestHandler>> * (^)(void))getHandlers
```

Right now, all id<RCTURLRequestHandler> are NativeModules. So, they need to be loaded using the Bridge/TurboModuleManager.

## Problem
The method [that constructs RCTNetworking](https://www.internalfb.com/code/fbsource/[6530647879a5e6d5edcfad029b39879c87e97bb3]/fbobjc/Apps/Wilde/FBReactModule2/FBReactModuleAPI/FBReactModuleAPI/FBReactModule.mm?lines=1471) is shared between bridge mode and bridgeless mode. So, the shared constructor needs to know what infra to use to load the request handlers: the TurboModuleManager, when called from a bridgeless context; the bridge, when called from a bridge context. There's no easy way to let this shared constructor know what context it's being called from. We could fork the constructor, but that's not very clean.

## Changes
In this refactor, RCTNetworking gives its _handlersProvider its RCTModuleRegistry. If the module was instantiated in bridgeless mode, RCTModuleRegistry will use the TurboModuleManager. If the module was instantiated in bridge mode, RCTModuleRegistry will use the bridge. Using RCTModuleRegistry allows the _handlersProvider to load id<RCTURLRequestHandler> from correct infra, in both contexts.

Changelog: [iOS][Changed] - Give RCTNetworking handler provider block RCTModuleRegistry

Reviewed By: PeteTheHeat

Differential Revision: D28013000

fbshipit-source-id: 956d660771ab18f5e7f24fcc28792f9a217146e7

Author: RSNara

Libraries/Network/RCTNetworking.h

@@ -31,7 +31,7 @@
  * Allows RCTNetworking instances to be initialized with handlers.
  * The handlers will be requested via the bridge's moduleForName method when required.
  */
-- (instancetype)initWithHandlersProvider:(NSArray<id<RCTURLRequestHandler>> * (^)(void))getHandlers;
+- (instancetype)initWithHandlersProvider:(NSArray<id<RCTURLRequestHandler>> * (^)(RCTModuleRegistry *))getHandlers;
 
 /**
  * Does a handler exist for the specified request?

Libraries/Network/RCTNetworking.mm

@@ -148,7 +148,7 @@ @implementation RCTNetworking
   NSMutableDictionary<NSNumber *, RCTNetworkTask *> *_tasksByRequestID;
   std::mutex _handlersLock;
   NSArray<id<RCTURLRequestHandler>> *_handlers;
-  NSArray<id<RCTURLRequestHandler>> * (^_handlersProvider)(void);
+  NSArray<id<RCTURLRequestHandler>> * (^_handlersProvider)(RCTModuleRegistry *);
   NSMutableArray<id<RCTNetworkingRequestHandler>> *_requestHandlers;
   NSMutableArray<id<RCTNetworkingResponseHandler>> *_responseHandlers;
 }
@@ -167,7 +167,7 @@ - (instancetype)init
   return [super initWithDisabledObservation];
 }
 
-- (instancetype)initWithHandlersProvider:(NSArray<id<RCTURLRequestHandler>> * (^)(void))getHandlers
+- (instancetype)initWithHandlersProvider:(NSArray<id<RCTURLRequestHandler>> * (^)(RCTModuleRegistry *moduleRegistry))getHandlers
 {
   if (self = [super initWithDisabledObservation]) {
     _handlersProvider = getHandlers;
@@ -209,7 +209,7 @@ - (void)invalidate
 
     if (!_handlers) {
       if (_handlersProvider) {
-        _handlers = _handlersProvider();
+        _handlers = _handlersProvider(self.moduleRegistry);
       } else {
         _handlers = [self.bridge modulesConformingToProtocol:@protocol(RCTURLRequestHandler)];
       }

packages/rn-tester/RNTester/AppDelegate.mm

@@ -215,7 +215,7 @@ - (Class)getModuleClassFromName:(const char *)name
           return @ [[RCTGIFImageDecoder new]];
         }];
   } else if (moduleClass == RCTNetworking.class) {
-    return [[moduleClass alloc] initWithHandlersProvider:^NSArray<id<RCTURLRequestHandler>> * {
+    return [[moduleClass alloc] initWithHandlersProvider:^NSArray<id<RCTURLRequestHandler>> *(RCTModuleRegistry * moduleRegistry) {
       return @[
         [RCTHTTPRequestHandler new],
         [RCTDataRequestHandler new],