Target C++ 17 (#38303)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/38303

X-link: https://github.com/facebook/yoga/pull/1327

This bumps Yoga to C++ 17 for a few reasons:
1. New versions of C++ may introduce behavior changes (e.g. evaluation order) and deprecations. Keeping the version closer to the version of large users helps avoid that.
2. C++ 17 unblocks some new bits I have wanted to use at times, like `std::optional`, `std::variant`, `if constexpr`, `[[nodiscard]]`.
3. There are already changes in C++ 20 that would be directly useful to Yoga, like `std::bit_cast` to avoid `memcpy` style type punning.

There has been some contention around C++ versions before, but by the time the next stable version of Yoga is out, it will have been more than 6 years (~2 C++ versions) since a stable version of Clang/LLVM with C++ 17 support. I would not like to go back further than n-2.

Changelog: [Internal]

Reviewed By: christophpurrer

Differential Revision: D47383922

fbshipit-source-id: eb95d4853f2168b68d6df5fddb797236eac55870

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 14)
+set(CMAKE_CXX_STANDARD 17)
 set(CMAKE_CXX_VISIBILITY_PRESET hidden)
 set(CMAKE_POSITION_INDEPENDENT_CODE ON)
 
@@ -33,6 +33,7 @@ add_compile_options(
     -fexceptions
     # Enable warnings and warnings as errors
     -Wall
+    -Wextra
     -Werror
     # Disable RTTI
     $<$<COMPILE_LANGUAGE:CXX>:-fno-rtti>