[clang][NFC] Add test for CWG1898 "Use of “equivalent” in overload resolution" (#113439)
[CWG1898](https://cplusplus.github.io/CWG/issues/1898.html) Use of
“equivalent” in overload resolution
====================
[P1787R6](https://wg21.link/p1787r6):
> CWG1898 is resolved by explicitly using the defined term
parameter-type-list.
Except that now it's called non-object-parameter-type-list, which is
defined in [dcl.fct] [p8](https://eel.is/c++draft/dcl.fct#8) and
[p4](https://eel.is/c++draft/dcl.fct#8).
As for the wording, the first sentence
[\_N4140\_.[over.dcl]/1](https://timsong-cpp.github.io/cppwp/n4140/over.dcl#1)
where the word "equivalent" was used:
> Two function declarations of the same name refer to the same function
if they are in the same scope and have equivalent parameter declarations
([over.load]).
was replaced with what is now known as "corresponding overloads",
defined in
[[basic.scope.scope]/4](https://eel.is/c++draft/basic.scope#scope-4).
The definition is present in P1787R6, but it's hard to reference,
because the "corresponding overloads" term was coined later.