Breaking: Use C++ 20 (facebook#39437)

Summary:
X-link: facebook/yoga#1382

Pull Request resolved: facebook#39437

Have been running into places where C++ 20 makes life easier for use like `std::bit_cast` (that one is easy to polyfill), in-class member initializer support for bitfields, designated initializers, defaulted comparison operator, concepts instead of SFINAE, and probably more.

Our other infra is in the process of making this jump, or already has. This tests it out everywhere, across the various reference builds, to see if we have any issues.

This is a bit more aggressive than I had previously communicated, but n - 1 is going to be a better long term place than n - 2.

Accounting for bundled STL, and using `bit_cast` as a reference feature, I think this means we require one of:
1. GCC 11+ (~2.5 years old)
1. Clang 14 (~2.5 years old)
1. VS 16.11 (~2 years old)

On mobile, the Clang 14 requirement translates to needing one of:
1. NDK 25 (~1 year old)
1. XCode 14.2.0 (~1 year old)

https://en.cppreference.com/w/cpp/compiler_support/20

I think it is likely everything will be buildable for a while under Clang 10 (released 3.5 years ago), GCC 11 (releaseed 3.5 years ago), and .

Anyone needing support for older C++ versions can lag behind on more recent changes. E.g. Yoga 2.0 supports C++ 14.

Differential Revision: https://internalfb.com/D49261607

fbshipit-source-id: f6eddcfdc9e21ffaf76a72b61fff319388342ded

packages/react-native/ReactCommon/yoga/Yoga.podspec

@@ -38,7 +38,7 @@ Pod::Spec.new do |spec|
       '-fexceptions',
       '-Wall',
       '-Werror',
-      '-std=c++17',
+      '-std=c++20',
       '-fPIC'
   ]
 

packages/react-native/ReactCommon/yoga/cmake/project-defaults.cmake

@@ -3,7 +3,7 @@
 # This source code is licensed under the MIT license found in the
 # LICENSE file in the root directory of this source tree.
 
-set(CMAKE_CXX_STANDARD 17)
+set(CMAKE_CXX_STANDARD 20)
 set(CMAKE_CXX_VISIBILITY_PRESET hidden)
 set(CMAKE_POSITION_INDEPENDENT_CODE ON)
 

packages/react-native/ReactCommon/yoga/yoga/bits/BitCast.h

@@ -14,6 +14,7 @@ namespace facebook::yoga {
 
 // Polyfill for std::bit_cast() from C++20, to allow safe type punning
 // https://en.cppreference.com/w/cpp/numeric/bit_cast
+// TODO: Remove when we upgrade to NDK 26+
 template <class To, class From>
 std::enable_if_t<
     sizeof(To) == sizeof(From) && std::is_trivially_copyable_v<From> &&