Address Qt 6.8 CMake API review notes for qtbase qt_wrap_cpp

*Action points:*
AP: Rewrite the docs for new signature to be a list instead of a paragraph
(or at least make it more readable)
AP: Look if we can implement the new signature
AP: Adjust the new signature snippet in the docs
AP: Should probably be two different signatures in the docs
AP: Recommend the new signature instead, more user friendly
AP: Investigate if we can show a warning when using old signature, or find a way
to accomodate the distinction between TARGET foo signature and first param ${target} signature