* Using -std=gnu++2b now for both gcc and clang as clang
does not recognize gnu++23 yet
* Added a build test app to check the C++ standard in IDF
* Updated english docs to reflect the change to C++23
In C++20, using the result of an assignment to a 'volatile' value is
deprecated.
Breaking change: register "setter" or modification macros can no
longer be used as expressions.
Closes https://github.com/espressif/esp-idf/issues/9170