enum class underlying types conversions

[Hind-M]

• Replace in codebase any conversions of existing enum classes by using ternary operator or static_cast by implementing C++23 utility function std::to_underlying.

cf. https://www.cppstories.com/2024/enum-improvements/#c23-stdto_underlying
cf. #3396 for an example of concerned enum class

• Add a comment to note that it should be replaced with the one from the standard library when supporting C++23.