[libc++] Give `MoveOnly` all six comparison operators, not just == and <.

Split out of D93512.

GitOrigin-RevId: fc3192026b3156d39c223cc092297c39dd8013f3
diff --git a/test/support/MoveOnly.h b/test/support/MoveOnly.h
index adcae25..61eb190 100644
--- a/test/support/MoveOnly.h
+++ b/test/support/MoveOnly.h
@@ -32,7 +32,11 @@
     constexpr int get() const {return data_;}
 
     constexpr bool operator==(const MoveOnly& x) const {return data_ == x.data_;}
+    constexpr bool operator!=(const MoveOnly& x) const {return data_ != x.data_;}
     constexpr bool operator< (const MoveOnly& x) const {return data_ <  x.data_;}
+    constexpr bool operator<=(const MoveOnly& x) const {return data_ <= x.data_;}
+    constexpr bool operator> (const MoveOnly& x) const {return data_ >  x.data_;}
+    constexpr bool operator>=(const MoveOnly& x) const {return data_ >= x.data_;}
     TEST_CONSTEXPR_CXX14 MoveOnly operator+(const MoveOnly& x) const
         { return MoveOnly{data_ + x.data_}; }
     TEST_CONSTEXPR_CXX14 MoveOnly operator*(const MoveOnly& x) const