4/n Display a RedBox with the JS stack (instead of native stack) when an unhandled JS exceptions occurs

Summary:
Changelog: [iOS][Changed] Display a RedBox with the JS stack (instead of native stack) when an unhandled JS exceptions occurs

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# A0) Bridge mode, Unhandled Exception, FBiOS
Unhandled exception goes to FBReactModule, but the JS Stack is not parsed correctly.
https://www.internalfb.com/code/fbsource/[312d5cbdd7278247a84619786b12a44c4400fcc0]/fbobjc/Apps/Wilde/FBReactModule2/FBReactModuleAPI/FBReactModuleAPI/Exported/FBReactModule.mm?lines=1488%2C1493

See `****** FBReactModule handleFatalError` in the logs P539306390, and compare with correct behavior in (A1) in the Test Plan.

https://pxl.cl/2h6h3

{F782257996}

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# A) Before diff, rn-tester
Open to rn-tester -> APIs -> Crash Examples -> JS Crash.

Set `RCTParseUnhandledJSErrorStackNatively` to YES.
https://www.internalfb.com/code/fbsource/[98880e52ee78be3614e5d9a2ce3292f6a7b5e413]/xplat/js/react-native-github/React/Base/RCTConstants.m?lines=73

{F783395297}

Reviewed By: sammy-SC

Differential Revision: D40387938

fbshipit-source-id: 2abea657476d3bf61ad5b1c643f129e44c6f3f35

ReactCommon/jserrorhandler/React-jserrorhandler.podspec

@@ -0,0 +1,36 @@
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+#
+# This source code is licensed under the MIT license found in the
+# LICENSE file in the root directory of this source tree.
+
+require "json"
+
+package = JSON.parse(File.read(File.join(__dir__, "..", "..", "package.json")))
+version = package['version']
+
+source = { :git => 'https://github.com/facebook/react-native.git' }
+if version == '1000.0.0'
+  # This is an unpublished version, use the latest commit hash of the react-native repo, which we’re presumably in.
+  source[:commit] = `git rev-parse HEAD`.strip if system("git rev-parse --git-dir > /dev/null 2>&1")
+else
+  source[:tag] = "v#{version}"
+end
+
+Pod::Spec.new do |s|
+  s.name                   = "React-jserrorhandler"
+  s.version                = version
+  s.summary                = "-"  # TODO
+  s.homepage               = "https://reactnative.dev/"
+  s.license                = package["license"]
+  s.author                 = "Facebook, Inc. and its affiliates"
+  s.platforms              = { :ios => "12.4", :tvos => "12.4" }
+  s.public_header_files    = [ "JsErrorHandler.h" ]
+  s.source                 = source
+  s.source_files           = "*.{cpp,h}"
+  s.pod_target_xcconfig    = { "HEADER_SEARCH_PATHS" => "" }
+  s.header_dir             = "jserrorhandler"
+
+  s.dependency "React-jsi", version
+  s.dependency "React-Fabric/mapbuffer", version
+
+end