* Define the concept of "parser" in X3
Also modernizes the entry points and the most fundamental "x3::parser"
base class.
Includes overhaul on `any_parser` as it operates on iterator/sentinal
now.
Deprecate `any_parser`. The reasoning is described in the comments.
* [X3] Bump C++ version to C++23
* Set correct compilers for C++23
* Avoid recursive instantiation on `unary_parser`
* Update Ubuntu 22.04 -> 24.04
* Specify correct flags for clang++/g++ detection
* Move deprecation warning of `any_parser` to its constructor
