New classes + improvements.

Added etl::result type
Added etl::byte_stream
Added denominated etl::to_string overloads
Added etl::remove_cvref to type traits
Replaced etl::remove_reference_t with etl::remove_cvref_t in variadic etl::variant
Added call_if and call_or member functions to etl::delegate
Improved compliance with MISRA rules
Extended 'successor' handling for all derived message router types