Resolve concept loops with functions
This MR replaces the lambda in unevaluated contexts with an explicit function. This makes the code more portable as there is no need for a compiler that supports [temp.deduct/9], for example, Apple Clang 15. Therefore, we can use concepts even when DUNE_HAVE_CXX_UNEVALUATED_CONTEXT_LAMBDA is false.
Edited by Santiago Ospina De Los Ríos