Add SRWebSocketProvider for selective WebSocket header injection (facebook#55870)

Summary:
Pull Request resolved: facebook#55870

## Summary:

Replace the blind application of dev headers on all WebSocket connections with
a provider pattern that mirrors RCTHTTPRequestHandler's
NSURLSessionConfigurationProvider. A custom `SRWebSocketProvider` block can be
registered via `RCTSetCustomSRWebSocketProvider` to intercept WebSocket
creation and selectively modify the request (e.g. injecting auth headers) for
specific endpoints. If no provider is set, or if the provider returns nil,
the default SRWebSocket creation logic is used.

- Declare `SRWebSocketProvider` typedef and `RCTSetCustomSRWebSocketProvider`
  in RCTWebSocketModule.h
- Implement the provider hook in RCTWebSocketModule.mm
- Remove the previous blind `RCTDevSupportHttpHeaders` application

## Changelog:

[IOS][CHANGED] - Add SRWebSocketProvider for selective WebSocket header injection

## Test Plan:

Verified that the `SRWebSocketProvider` block is called when registered, and
that returning nil falls back to the default SRWebSocket creation. When no
provider is registered, behavior is unchanged from before.

## Facebook:
Applied from nest/mobile/apps/atod-sample/patches/react-native+0.83.1+005+atod-websocket-ios.patch

Reviewed By: cortinico

Differential Revision: D95037876

fbshipit-source-id: 8e721397802db6eac9df686b0d064f597747a746

Author: cipolleschi

packages/react-native/React/CoreModules/RCTWebSocketModule.h

@@ -18,6 +18,12 @@ NS_ASSUME_NONNULL_BEGIN
 
 @end
 
+@class SRWebSocket;
+
+typedef SRWebSocket * (^SRWebSocketProvider)(NSURLRequest *request);
+
+RCT_EXTERN void RCTSetCustomSRWebSocketProvider(SRWebSocketProvider provider);
+
 @interface RCTWebSocketModule : RCTEventEmitter
 
 // Register a custom handler for a specific websocket. The handler will be strongly held by the WebSocketModule.

packages/react-native/React/CoreModules/RCTWebSocketModule.mm

@@ -35,6 +35,13 @@ @interface RCTWebSocketModule () <SRWebSocketDelegate, NativeWebSocketModuleSpec
 
 @end
 
+static SRWebSocketProvider srWebSocketProvider;
+
+void RCTSetCustomSRWebSocketProvider(SRWebSocketProvider provider)
+{
+  srWebSocketProvider = provider;
+}
+
 @implementation RCTWebSocketModule {
   NSMutableDictionary<NSNumber *, SRWebSocket *> *_sockets;
   NSMutableDictionary<NSNumber *, id<RCTWebSocketContentHandler>> *_contentHandlers;
@@ -114,7 +121,13 @@ - (void)invalidate
     }];
   }
 
-  SRWebSocket *webSocket = [[SRWebSocket alloc] initWithURLRequest:request protocols:protocols];
+  SRWebSocket *webSocket;
+  if (srWebSocketProvider != nullptr) {
+    webSocket = srWebSocketProvider(request);
+  }
+  if (webSocket == nil) {
+    webSocket = [[SRWebSocket alloc] initWithURLRequest:request protocols:protocols];
+  }
   [webSocket setDelegateDispatchQueue:[self methodQueue]];
   webSocket.delegate = self;
   webSocket.reactTag = @(socketID);