build backwards compat API for runtime pointer

Summary:
Changelog: [iOS][Added]

This is a pre-deprecated API to give access to the jsi::Runtime in iOS in bridgeless. In bridge, this value is a private selector on RCTBridge that is exposed via category. We build this into the backwards compatible RCTBridgeProxy here.

This should work out of the box in bridgeless if you are already retrieveing the pointer via the bridge. However, we recommend users to eventually migrate towards C++ TurboModule or the RuntimeExecutor if possible. This will be removed in the future.

changes as proposed in https://fb.workplace.com/groups/2158787827656681/posts/2306281142907348

Differential Revision: D53646413

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

@@ -20,7 +20,8 @@
                        bundleManager:(RCTBundleManager *)bundleManager
                    callableJSModules:(RCTCallableJSModules *)callableJSModules
                   dispatchToJSThread:(void (^)(dispatch_block_t))dispatchToJSThread
-               registerSegmentWithId:(void (^)(NSNumber *, NSString *))registerSegmentWithId NS_DESIGNATED_INITIALIZER;
+               registerSegmentWithId:(void (^)(NSNumber *, NSString *))registerSegmentWithId
+                             runtime:(void *)runtime NS_DESIGNATED_INITIALIZER;
 
 - (NSMethodSignature *)methodSignatureForSelector:(SEL)sel;
 - (void)forwardInvocation:(NSInvocation *)invocation;

packages/react-native/React/Base/RCTBridgeProxy.mm

@@ -28,6 +28,7 @@ @implementation RCTBridgeProxy {
   RCTCallableJSModules *_callableJSModules;
   void (^_dispatchToJSThread)(dispatch_block_t);
   void (^_registerSegmentWithId)(NSNumber *, NSString *);
+  void *_runtime;
 }
 
 - (instancetype)initWithViewRegistry:(RCTViewRegistry *)viewRegistry
@@ -36,15 +37,17 @@ - (instancetype)initWithViewRegistry:(RCTViewRegistry *)viewRegistry
                    callableJSModules:(RCTCallableJSModules *)callableJSModules
                   dispatchToJSThread:(void (^)(dispatch_block_t))dispatchToJSThread
                registerSegmentWithId:(void (^)(NSNumber *, NSString *))registerSegmentWithId
+                             runtime:(void *)runtime
 {
   self = [super self];
   if (self) {
-    self->_uiManagerProxy = [[RCTUIManagerProxy alloc] initWithViewRegistry:viewRegistry];
-    self->_moduleRegistry = moduleRegistry;
-    self->_bundleManager = bundleManager;
-    self->_callableJSModules = callableJSModules;
-    self->_dispatchToJSThread = dispatchToJSThread;
-    self->_registerSegmentWithId = registerSegmentWithId;
+    _uiManagerProxy = [[RCTUIManagerProxy alloc] initWithViewRegistry:viewRegistry];
+    _moduleRegistry = moduleRegistry;
+    _bundleManager = bundleManager;
+    _callableJSModules = callableJSModules;
+    _dispatchToJSThread = dispatchToJSThread;
+    _registerSegmentWithId = registerSegmentWithId;
+    _runtime = runtime;
   }
   return self;
 }
@@ -75,10 +78,10 @@ - (Class)executorClass
  * Used By:
  *  - RCTBlobCollector
  */
-- (jsi::Runtime *)runtime
+- (void *)runtime
 {
-  [self logWarning:@"This method is unsupported. Returning nullptr." cmd:_cmd];
-  return nullptr;
+  [self logWarning:@"Please migrate to C++ TurboModule or RuntimeExecutor." cmd:_cmd];
+  return _runtime;
 }
 
 /**
@@ -162,7 +165,7 @@ - (void)enqueueJSCall:(NSString *)module
 
 - (void)registerSegmentWithId:(NSUInteger)segmentId path:(NSString *)path
 {
-  self->_registerSegmentWithId(@(segmentId), path);
+  _registerSegmentWithId(@(segmentId), path);
 }
 
 - (id<RCTBridgeDelegate>)delegate