fixup! [libc++][NFC] Centralize test for support of == and != in ranges

Addressing final feedback and consolidating one final spot.

Author: hawkinsw

libcxx/test/std/ranges/range.adaptors/range.take/range.take.sentinel/eq.pass.cpp

@@ -21,6 +21,7 @@
 
 #include "test_comparisons.h"
 #include "test_iterators.h"
+#include "test_range.h"
 
 template <bool Const>
 using MaybeConstIterator = cpp20_input_iterator<std::conditional_t<Const, const int*, int*>>;
@@ -77,14 +78,6 @@ struct NonCrossConstComparableView : std::ranges::view_base {
 static_assert(std::ranges::range<NonCrossConstComparableView>);
 static_assert(std::ranges::range<const NonCrossConstComparableView>);
 
-template <class T, class U>
-concept weakly_equality_comparable_with = requires(const T& t, const U& u) {
-  t == u;
-  t != u;
-  u == t;
-  u != t;
-};
-
 constexpr bool test() {
   int buffer[8]                      = {1, 2, 3, 4, 5, 6, 7, 8};
   using CrossConstComparableTakeView = std::ranges::take_view<CrossConstComparableView>;

libcxx/test/support/test_range.h

@@ -96,6 +96,7 @@ concept CanBePiped = requires(View&& view, T&& t) {
   { std::forward<View>(view) | std::forward<T>(t) };
 };
 
+// See [concept.equalitycomparable]
 template <class T, class U>
 concept weakly_equality_comparable_with =
     requires(const std::remove_reference_t<T>& t, const std::remove_reference_t<U>& u) {