C++26: Cleaning up string literals

The two papers we are covering today are complementary in a philosophical sense. They both improve how string literals are handled in C++26. P2361R6 tackles strings that are never evaluated — the ones that only exist at compile time. P1854R4 tackles evaluated string literals, making non-encodable characters ill-formed instead of implementation-defined. Let’s start with the unevaluated side. ...